Apparatus and method for operating user plane protocol stack in connectionless communication system

ABSTRACT

The present disclosure relates to a pre-5th-generation (5G) or 5G communication system to be provided for supporting higher data rates beyond 4th-generation (4G) communication system such as a long term evolution (LTE). A method for communication by a base station is provided. The method includes transmitting a scheduling assignment including a first part of a destination identifier (ID), and transmitting a medium access control (MAC) protocol data unit (PDU) including a MAC header including a user equipment (UE) ID and a second part of the destination ID.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 16/439,189, filed on Jun. 12, 2019; which is a continuationapplication of prior application Ser. No. 15/112,370, filed on Jul. 18,2016, which is a U.S. National Stage application under 35 U.S.C. § 371of an International Patent Application filed on Jan. 16, 2015 andassigned application number PCT/KR2015/000497, which has issued as U.S.Pat. No. 10,485,018 on Nov. 19, 2019, which claimed the benefit of anIndian Patent Application filed Jan. 16, 2014 in the Indian IntellectualProperty Office and assigned Serial number 68/KOL/2014, an Indian PatentApplication filed Mar. 4, 2014 in the Indian Intellectual PropertyOffice and assigned Serial number 265/KOL/2014 and an Indian PatentApplication filed Jul. 18, 2014 in the Indian Intellectual PropertyOffice and assigned the application number 772/KOL/2014, the entiredisclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to an apparatus and method for operatinga user plane protocol stack in a connectionless communication system.

BACKGROUND

To meet the demand for wireless data traffic, which has increased sincedeployment of 4th-generation (4G) communication systems, efforts havebeen made to develop an improved 5th-generation (5G) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘beyond 4G network’ or a ‘post long-term evolution(LTE) system’.

It is considered that the 5G communication system will be implemented inmillimeter wave (mmWave) bands, e.g., 60 GHz bands, so as to accomplishhigher data rates. To reduce propagation loss of radio waves andincrease a transmission distance, a beam forming technique, a massivemultiple-input multiple-output (MIMO) technique, a full dimensional MIMO(FD-MIMO) technique, an array antenna technique, an analog beam formingtechnique, and a large scale antenna technique are discussed in 5Gcommunication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud radioaccess networks (RANs), ultra-dense networks, a D2D communication, awireless backhaul, a moving network, a cooperative communication,coordinated multi-points (CoMP), reception-end interferencecancellation, and the like.

In the 5G system, a hybrid frequency shift keying (FSK) and quadratureamplitude modulation (QAM) modulation (FQAM) and a sliding windowsuperposition coding (SWSC) as an advanced coding modulation (ACM)scheme, and a filter bank multi carrier (FBMC) scheme, a non-orthogonalmultiple Access (NOMA) scheme, and a sparse code multiple access (SCMA)scheme as an advanced access technology have been developed.

In a conventional connection oriented wireless communication system,data radio bearers are established by explicit signaling between a userequipment (UE) and a base station (BS).

Applications or internet protocol (IP) flows with different quality ofservice (QoS) are mapped to different radio bearers.

A user plane protocol stack for data transmission/reception includes apacket data convergence protocol (PDCP) layer entity, a radio linkcontrol (RLC) layer entity, and a medium access control (MAC) layerentity.

Each radio bearer's data is processed by an independent PDCP layerentity and an independent RLC layer entity which are configured attiming of radio bearer establishment by explicit signaling. The radiobearer is identified by a radio bearer identity (RB ID). The MAC layerentity is common across all radio bearers of a UE. The PDCP layer entityand the RLC layer entity with appropriate parameters are configured andestablished at the UE and a BS at timing of radio bearer establishment.Each radio bearer is mapped to a logical channel in a MAC layer. Thelogical channel is identified using a logical channel identifier (LCID).The LCID is assigned by the BS during a radio bearer establishmentprocess. A set of LCIDs from which a LCID is assigned to a radio beareris specific to the UE. The same set of LCIDs is reused in other UEs.

An identification of a logical channel associated with a radio bearer ina conventional connection oriented wireless communication system will bedescribed with reference to FIG. 1.

FIG. 1 schematically illustrates an identification of a logical channelassociated with a radio bearer in a conventional connection orientedwireless communication system.

Referring to FIG. 1, the connection oriented wireless communicationsystem includes a BS 111, a UE #1 113, and a UE #2 115.

In a downlink direction (i.e., a BS to a UE), the BS includes an LCIDinto a MAC header of a MAC protocol data unit (PDU) which carries a datapacket or a MAC service data unit (SDU) for a related radio bearer. MACPDUs which are specific to the UE are generated as physical layer entitypackets, and the physical layer entity packets are transmitted to the UEthrough a radio resource which is specific to the UE by a physical layerentity in the BS.

In the UE side, the physical layer entity receives and decodes thephysical layer entity packets through the radio resource which isspecific to the UE, and transmits the MAC PDUs to a MAC layer entity.The MAC layer entity transmits the MAC SDUs received in the MAC PDUs tothe RLC layer entity of related radio bearer based on an LCID includedin the MAC header.

In a uplink direction (i.e., a UE to a BS), the UE includes the LCIDinto a MAC header in which a MAC PDU which carries a data packet or aMAC SDU of a related radio bearer is included. In the uplink direction,the BS receives MAC PDUs from a plurality of UEs. The BS identifies UEassociated with a received MAC PDU based on the allocated uplinkresource. Here, a resource in the uplink is allocated by the BS to eachUE. The BS transmits the MAC SDU(s) received in the MAC PDU to the RLClayer entity of a related radio bearer for a UE which is identifiedbased on an LCID included in the MAC header.

Meanwhile, device to device (D2D) broadcast/group cast communicationenables a UE to concurrently transmit the same information to aplurality of different UEs in proximity of the UE. A D2D broadcastchannel may be used by a transmitter to transmit information to all UEsin proximity of the transmitter, or to transmit information to aspecific UE or UEs included in a specific group.

From a physical channel, each broadcast channel is the same irrespectiveof broadcast, unicast or multicast of information which is transmittedby the transmitter. Further, D2D communication is also connectionless.That is, in the D2D communication, there is no explicit signalingbetween communicating devices for establishing a connection.

A user plane protocol stack for data transmission/reception for the D2Dcommunication also includes a PDCP layer entity, a RLC layer entity, anda MAC layer entity.

In the connectionless D2D communication, key issues regardingconfiguration of a user plane protocol stack in a transmitter and areceiver are as the following.

The first issue is how to establish and configure radio bearers and alogical channel in a connectionless approach.

The second issue is how many radio bearers are configured in atransmitter/receiver and when.

The third issue is how to identify a radio bearer in a transmitter and areceiver.

So, there is a need of operating a user plane protocol stack byconsidering the above issues in a connectionless communication system.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present disclosure.

SUMMARY

An aspect of the present disclosure is to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentdisclosure is to propose an apparatus and method for operating a userplane protocol stack in a connectionless communication system.

Another aspect of the present disclosure is to propose an apparatus andmethod for operating a user plane protocol stack by considering a radiobearer in a connectionless communication system.

Another aspect of the present disclosure is to propose an apparatus andmethod for operating a user plane protocol stack by considering alogical channel in a connectionless communication system.

Another aspect of the present disclosure is to propose an apparatus andmethod for operating a user plane protocol stack based on a source IDand a destination ID in a connectionless communication system.

Another aspect of the present disclosure is to propose an apparatus andmethod for operating a user plane protocol stack based on a transmissionsession type in a connectionless communication system.

Another aspect of the present disclosure is to propose an apparatus andmethod for operating a user plane protocol stack by considering datacompression in a connectionless communication system.

In accordance with an aspect of the present disclosure, a method forcommunication by a base station is provided. The method includesdividing a destination ID into a first part and a second part,transmitting a scheduling assignment including a first part of thedestination ID, and transmitting a medium access control (MAC) protocoldata unit (PDU) including a UE identifier and a second part of thedestination ID in a MAC header of the MAC PDU.

In accordance with another aspect of the present disclosure, a methodfor communication by a user equipment (UE) is provided. The methodincludes receiving a scheduling assignment; receiving a medium accesscontrol (MAC) protocol data unit (PDU); determining whether the receivedMAC PDU is destined for the UE; determining whether there is a packetdata convergence protocol (PDCP) layer entity and a radio link control(RLC) layer entity for data reception corresponding to a MAC servicedata unit (SDU) received in the MAC PDU destined for the UE;establishing a new PDCP layer entity and a new RLC layer entity for datareception corresponding to the MAC SDU, if the PDCP layer entity and theRLC layer entity for data reception corresponding to the MAC SDUreceived in the MAC PDU is not already established; and delivering theMAC SDU to an RLC layer entity corresponding to a source UE ID, alogical channel identifier (LCID), and a destination ID of the MAC SDUfor processing.

In accordance with still another aspect of the present disclosure, anapparatus for communication being adapted to perform the method isprovided.

In accordance with still another aspect of the present disclosure, amethod for communication by a base station is provided. The methodincludes transmitting a scheduling assignment including a first part ofa destination identifier (ID); and transmitting a medium access control(MAC) protocol data unit (PDU) including a MAC header including a userequipment (UE) ID and a second part of the destination ID.

In accordance with still another aspect of the present disclosure, amethod for communication by a user equipment (UE) is provided. Themethod includes receiving a scheduling assignment; receiving a mediumaccess control (MAC) protocol data unit (PDU); determining whether thereceived MAC PDU is destined for the UE; determining whether there is apacket data convergence protocol (PDCP) layer entity and a radio linkcontrol (RLC) layer entity for data reception corresponding to a MACservice data unit (SDU) included in the MAC PDU if the received MAC PDUis destined for the UE; establishing a new PDCP layer entity and a newRLC layer entity for data reception corresponding to the MAC SDU, ifthere are no PDCP layer entity and RLC layer entity for data receptioncorresponding to the MAC SDU; and delivering the MAC SDU to an RLC layerentity corresponding to a source UE identifier (ID), a logical channelidentifier (LCID), and a destination ID of the MAC SDU for processing.

In accordance with still another aspect of the present disclosure, abase station is provided. The base station includes a processorconfigured to transmit a scheduling assignment including a first part ofa destination identifier (ID), and transmit a medium access control(MAC) protocol data unit (PDU) including a MAC header including a userequipment (UE) ID and a second part of the destination ID.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the disclosure.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document: the terms “include” and “comprise,” aswell as derivatives thereof, mean inclusion without limitation; the term“or,” is inclusive, meaning and/or; the phrases “associated with” and“associated therewith, “as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like; and the term “controller”means any device, system or part thereof that controls at least oneoperation, such a device may be implemented in hardware, firmware orsoftware, or some combination of at least two of the same. It should benoted that the functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely.Definitions for certain words and phrases are provided throughout thispatent document, those of ordinary skill in the art should understandthat in many, if not most instances, such definitions apply to prior, aswell as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of certainexemplary embodiments of the present disclosure will be more apparentfrom the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 schematically illustrates an identification of a logical channelassociated with a radio bearer in a conventional connection orientedwireless communication system;

FIG. 2 schematically illustrates an example of a structure of a userplane protocol stack for a data transmission and reception which isbased on a user plane protocol stack configuration scheme #1 in aconnectionless communication system according to an embodiment of thepresent disclosure;

FIG. 3 schematically illustrates another example of a structure of auser plane protocol stack for a data transmission and which is based ona user plane protocol stack configuration scheme #1 in a connectionlesscommunication system according to an embodiment of the presentdisclosure;

FIG. 4 schematically illustrates an example of a structure of a userplane protocol stack for a data transmission and reception which isbased on a user plane protocol stack configuration scheme #2 in aconnectionless communication system according to an embodiment of thepresent disclosure;

FIGS. 5A and 5B schematically illustrate another example of a structureof a user plane protocol stack for data transmission and reception whichis based on a user plane protocol stack configuration scheme #2 in aconnectionless communication system according to an embodiment of thepresent disclosure;

FIG. 6 schematically illustrates an example of a structure of a userplane protocol stack for a data transmission and reception which isbased on a user plane protocol stack configuration scheme #3 in aconnectionless communication system according to an embodiment of thepresent disclosure;

FIGS. 7A and 7B schematically illustrate another example of a structureof a user plane protocol stack for a data transmission and receptionwhich is based on a user plane protocol stack configuration scheme #3 ina connectionless communication system according to an embodiment of thepresent disclosure;

FIG. 8 schematically illustrates an example of a format of a MACsub-header indicating a source UE ID and a destination ID in aconnectionless communication system according to an embodiment of thepresent disclosure;

FIG. 9A schematically illustrates a format of a MAC sub-headerindicating a source UE ID in a connectionless communication systemaccording to an embodiment of the present disclosure;

FIG. 9B schematically illustrates a format of a MAC sub-headerindicating a destination ID in a connectionless communication systemaccording to an embodiment of the present disclosure;

FIG. 10 schematically illustrates an example of a format of a MAC headerindicating a source UE ID and a destination ID in a connectionlesscommunication system according to an embodiment of the presentdisclosure;

FIG. 11A schematically illustrates another example of a format of a MACheader indicating a source UE ID and a destination ID in aconnectionless communication system according to an embodiment of thepresent disclosure;

FIG. 11B schematically illustrates still another example of a format ofa MAC header indicating a source UE ID and a destination ID in aconnectionless communication system according to an embodiment of thepresent disclosure;

FIG. 12 schematically illustrates another example of a format of a MACsub-header indicating a source UE ID and a destination ID in aconnectionless communication system according to an embodiment of thepresent disclosure;

FIG. 13 schematically illustrates still another example of a format of aMAC sub-header indicating a source UE ID and a destination ID in aconnectionless communication system according to an embodiment of thepresent disclosure;

FIG. 14 schematically illustrates an inner structure of a BS in aconnectionless communication system according to an embodiment of thepresent disclosure; and

FIG. 15 schematically illustrates an inner structure of a UE in aconnectionless communication system according to an embodiment of thepresent disclosure.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the present disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thepresent disclosure. In addition, descriptions of well-known functionsand constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of the presentdisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of the presentdisclosure is provided for illustration purpose only and not for thepurpose of limiting the present disclosure as defined by the appendedclaims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

Although ordinal numbers such as “first,” “second,” and so forth will beused to describe various components, those components are not limitedherein. The terms are used only for distinguishing one component fromanother component. For example, a first component may be referred to asa second component and likewise, a second component may also be referredto as a first component, without departing from the teaching of theinventive concept. The term “and/or” used herein includes any and allcombinations of one or more of the associated listed items.

The terminology used herein is for the purpose of describing variousembodiments only and is not intended to be limiting. As used herein, thesingular forms are intended to include the plural forms as well, unlessthe context clearly indicates otherwise. It will be further understoodthat the terms “comprises” and/or “has,” when used in thisspecification, specify the presence of a stated feature, number, step,operation, component, element, or combination thereof, but do notpreclude the presence or addition of one or more other features,numbers, steps, operations, components, elements, or combinationsthereof.

The terms used herein, including technical and scientific terms, havethe same meanings as terms that are generally understood by thoseskilled in the art, as long as the terms are not differently defined. Itshould be understood that terms defined in a generally-used dictionaryhave meanings coinciding with those of terms in the related technology.

According to various embodiments of the present disclosure, anelectronic device may include communication functionality. For example,an electronic device may be a smart phone, a tablet personal computer(PC), a mobile phone, a video phone, an e-book reader, a desktop PC, alaptop PC, a netbook PC, a personal digital assistant (PDA), a portablemultimedia player (PMP), an mp3 player, a mobile medical device, acamera, a wearable device (e.g., a head-mounted device (HMD), electronicclothes, electronic braces, an electronic necklace, an electronicappcessory, an electronic tattoo, or a smart watch), and/or the like.

According to various embodiments of the present disclosure, anelectronic device may be a smart home appliance with communicationfunctionality. A smart home appliance may be, for example, a television,a digital video disk (DVD) player, an audio, a refrigerator, an airconditioner, a vacuum cleaner, an oven, a microwave oven, a washer, adryer, an air purifier, a set-top box, a TV box (e.g., SamsungHomeSync™, Apple TV™, or Google TV™), a gaming console, an electronicdictionary, an electronic key, a camcorder, an electronic picture frame,and/or the like.

According to various embodiments of the present disclosure, anelectronic device may be a medical device (e.g., magnetic resonanceangiography (MRA) device, a magnetic resonance imaging (MRI) device,computed tomography (CT) device, an imaging device, or an ultrasonicdevice), a navigation device, a global positioning system (GPS)receiver, an event data recorder (EDR), a flight data recorder (FDR), anautomotive infotainment device, a naval electronic device (e.g., navalnavigation device, gyroscope, or compass), an avionic electronic device,a security device, an industrial or consumer robot, and/or the like.

According to various embodiments of the present disclosure, anelectronic device may be furniture, part of a building/structure, anelectronic board, electronic signature receiving device, a projector,various measuring devices (e.g., water, electricity, gas orelectro-magnetic wave measuring devices), and/or the like that includecommunication functionality.

According to various embodiments of the present disclosure, anelectronic device may be any combination of the foregoing devices. Inaddition, it will be apparent to one having ordinary skill in the artthat an electronic device according to various embodiments of thepresent disclosure is not limited to the foregoing devices.

According to various embodiments of the present disclosure, for example,a user equipment (UE) may be an electronic device.

An embodiment of the present disclosure proposes an apparatus and methodfor operating a user plane protocol stack in a connectionlesscommunication system.

An embodiment of the present disclosure proposes an apparatus and methodfor operating a user plane protocol stack by considering a radio bearerin a connectionless communication system.

An embodiment of the present disclosure proposes an apparatus and methodfor operating a user plane protocol stack by considering a logicalchannel in a connectionless communication system.

An embodiment of the present disclosure proposes an apparatus and methodfor operating a user plane protocol stack based on a source UEidentifier (ID) and a destination ID in a connectionless communicationsystem.

An embodiment of the present disclosure proposes an apparatus and methodfor operating a user plane protocol stack based on a transmissionsession type in a connectionless communication system.

An embodiment of the present disclosure proposes an apparatus and methodfor operating a user plane protocol stack by considering datacompression in a connectionless communication system.

An embodiment of the present disclosure proposes three schemes for userplane protocol stack configuration, i.e., a user plane protocol stackconfiguration scheme #1, a user plane protocol stack configurationscheme #2 and a user plane protocol stack configuration scheme #3, andthis will be described below.

Firstly, a user plane protocol stack configuration scheme #1 will bedescribed below.

A user plane protocol stack configuration scheme #1 for a datatransmission in a D2D communication system will be described below.

A UE which transmits data to one or more UEs may maintain a radio bearerfor D2D data transmission. The radio bearer includes a packet dataconvergence protocol (PDCP) layer entity and a radio link control (RLC)entity. The UE performs a transmission session (that is, a TX session)at a time during which the UE performs one of a broadcast session, agroup cast session, a unicast session at a time. The radio bearer ismapped to a logical channel, and the logical channel is mapped to a D2Dcommunication transport channel which is mapped to a D2D communicationphysical channel.

The radio bearer (i.e. the PDCP layer entity and the RLC layer entity)for the data transmission is established or created when the upper layerentity triggers a data transmission in a UE. The upper layer entity maybe a Prefix Routing over Set Elements (ProSe) Protocol entity or aApplication Protocol entity. The PDCP layer entity and the RLC layerentity are established or created and configured using default values.

The upper layer entity may indicate whether the data transmission in theUE is a broadcast transmission, a unicast transmission, or a group casttransmission. That is, the upper layer entity may indicate the datatransmission in the UE is the broadcast transmission, the unicasttransmission, or the group cast transmission by transmitting informationwhich indicates that the data transmission in the UE is the broadcasttransmission, the unicast transmission, or the group cast transmission.If the data transmission is the unicast transmission then the upperlayer entity provides the destination UE ID. If the data transmission isthe groupcast transmission, then upper layer provides the destinationGroup ID. The UE ID of the UE may also be provided by the upper layerentity.

The established/created PDCP layer entity and RLC layer entity arereleased if the upper layer entity stops the data transmission orinitiates a new data transmission session to a new destination. In theUE, a radio bearer (i.e. a PDCP layer entity and a RLC layer entity)which is established/created for a data transmission is released if theupper layer entity determines to release the radio bearer (i.e. the PDCPlayer entity and the RLC layer entity) which is established/created forthe data transmission.

The radio bearer (i.e. the PDCP layer entity and the RLC layer entity)in the transmitting UE (that is, TX UE) is identified by a destinationID, wherein the destination ID identifies the destination of data beingtransmitted. The destination ID can be at least one of a broadcast ID ora group ID or a UE ID. Alternately, the radio bearer (i.e. the PDCPlayer entity and the RLC layer entity) in the transmitting UE for datatransmission belong to a group may be identified by a transmitting UE ID& a destination Group ID.

During the data transmission, the PDCP layer entity processes packets(i.e. applies at least one of a security, a header compression, and asequence numbering to the packets), the packets received from upperlayer are sent to the RLC layer entity. The RLC layer processes thesepackets (i.e, applies at least one of a sequence numbering, and afragmentation to these packets (i.e. RLC SDUs)) and sends them to a MAClayer entity. The MAC layer entity transmits one or more of thesepackets (i.e. MAC SDUs) corresponding to the same destination ID in theMAC PDU.

During the data transmission, the UE includes a source identifier fieldin a MAC header of the MAC PDU. The source identifier field carries anidentity of a source of the MAC PDU. The source identifier field is setby the transmitting UE to its UE ID. Alternately, the source identifierfield is set to a part of its UE ID. If the size of UE ID is m bits, thepart of the UE ID may be n bits among the m bits, the n bits may beleast significant bits (LSBs). Here, n is less than m (n<m). The n bitsmay be most significant bits (MSBs). If the source identifier field isset to a part of the UE ID, whether the part of the UE ID is n LSBs or nMSBs of m bits UE ID may be pre-defined in the communication system.

In some D2D communication systems, scheduling assignment information maybe transmitted by a UE which transmits data. The scheduling assignmentinformation is transmitted before a MAC PDU which carries the data istransmitted. The remaining part of the UE ID which is not included inthe MAC header of the MAC PDU is included in the scheduling assignmentinformation transmitted by the UE prior to data transmission. Theremaining part of the UE ID which is not included in the MAC header ofthe MAC PDU may be included in a Cyclic Redundancy Check (CRC) mask ofthe scheduling assignment information. Alternately, the sourceidentifier field included in the MAC header may be a shortened UE ID.For example, the UE ID is shortened using a hashing function.

During the data transmission, the UE includes the destination identifierfield in MAC header. The destination identifier field carries theidentity of the destination of MAC PDU. The destination identifier fieldis set to destination ID. The destination ID may be a broadcast ID, aunicast ID, or a group ID of a group. Alternately destination identifierfield is set toa part of the destination ID. If the size of destinationID is m bits, the part of the destination ID may be n bits among the mbits, the n bits may be least significant bits (LSBs). Here, n is lessthan m (n<m). The n bits may be most significant bits (MSBs). If thedestination identifier field is set to part of the destination ID,whether the part of the destination ID is n LSBs or n MSBs of m bitsdestination ID may be pre-defined in the communication system.

In some D2D communication systems, scheduling assignment information maybe transmitted by a UE which transmits data. The scheduling assignmentinformation is transmitted before a MAC PDU which carries the data istransmitted. The remaining part of the destination ID which is notincluded in the MAC header of the MAC PDU is included in the schedulingassignment information transmitted by the UE prior to data transmission.The remaining part of the destination ID which is not included in a MACheader of the MAC PDU may be included in CRC mask of the schedulingassignment information.

Alternatively, the destination ID or the part of destination ID may beincluded in a CRC by masking the CRC with the destination ID or the partof the destination ID. Alternatively, the part of the destination ID maybe included in the CRC by masking the CRC with the destination ID, and aremaining part of the destination ID may be included in the MAC header.The CRC is included in a physical layer entity packet which carries aMAC protocol data unit (PDU).

If pre-filtering for packets in the MAC layer entity is not required,and/or if a security scheme is not applied at a radio bearer level,i.e., in the PDCP layer entity or the MAC layer entity, the destinationID or the part of the destination ID may not be required in the MACheader or the CRC mask.

A broadcast indicator bit may be included in the MAC header. Here, thebroadcast indicator bit may be implemented with 1 bit. For example, if avalue of the broadcast indicator bit is set to 0, it means that adestination ID, i.e., a unicast ID, a group cast ID, or a part of thedestination ID may be included in the MAC header. If the value of thebroadcast indicator bit is not set to 0, that is, the value of thebroadcast indicator bit is set to 1, it means that the destination ID(i.e., the unicast ID or the group cast ID), or the part of thedestination ID may not be included in the MAC header.

The broadcast indicator bit, and the destination ID or the part of thedestination ID (i.e., the unicast ID, the group cast ID, a part of theunicast ID, or a part of the group cast ID) may be included in a CRCmask instead of the MAC header. If the pre-filtering for the packets inthe MAC layer entity is not required, and/or if the security scheme isnot applied at the radio bearer level (i.e., in the PDCP layer entity orthe MAC layer entity), the broadcast indicator bit, and the destinationID or the part of the destination ID (i.e., the unicast ID, the groupcast ID, the part of the unicast ID, or the part of the group cast ID)may not be required in the MAC header or the CRC mask.

In some communication systems, scheduling assignment information may betransmitted by a UE which transmits data. The scheduling assignmentinformation is transmitted before a MAC PDU which carries the data istransmitted. In the communication systems, a source UE ID, i.e., a fullsource UE ID, a partial source UE ID, or a shortened source UE ID, and adestination ID, i.e., a full destination ID, a partial destination ID,or a shortened destination ID may be encoded in the schedulingassignment information.

A process of encoding the source UE ID and the destination ID will bedescribed below.

Firstly, the source UE ID is included as a field in schedulingassignment information. The destination ID is encoded in a CRC includedin the scheduling assignment information. Here, a CRC mask includes thedestination ID.

Secondly, at least one of the source UE ID and the destination ID isincluded as a field in the scheduling assignment information.

Thirdly, the destination UE ID is included as a field in the schedulingassignment information. The source UE ID is encoded in a CRC included inthe scheduling assignment information. Here, a CRC mask includes thesource ID.

Meanwhile, a control indicator may be included in the MAC header. Thecontrol indicator may be implemented with c bits. In an embodiment ofthe present disclosure, it will be assumed that the control indicator isimplemented with 2 bits. The control indicator may indicate whether aMAC PDU is broadcasted, unicasted, or group casted.

Firstly, if the control indicator indicates that the MAC PDU isbroadcasted, the source UE ID and the destination ID are not included inthe MAC header.

Secondly, if the control indicator indicates that the MAC PDU is groupcasted, the source UE ID or a part of the source UE ID, and a group IDis included in the MAC header.

Thirdly, if the control indicator indicates that the MAC PDU isunicasted, the source UE ID or the part of the source UE ID, and thedestination ID or a part of the destination ID are included in the MACheader. The part of the source UE ID may be a shortened source UE ID,and the shortened source UE ID is generated by shortening the source UEID using a hashing function. The group ID and an individual ID areassigned to UEs from independent address spaces. The control indicatorand the destination ID, i.e., a unicast ID, a group cast ID, a part ofthe unicast ID, or a part of the group cast ID may be included in a CRCmask instead of the MAC header.

A user plane protocol stack configuration scheme #1 for a datatransmission has been described above, and a user plane protocol stackconfiguration scheme #1 for a data reception will be described below.

The user plane protocol stack configuration scheme #1 for the datareception is based on one of the first implementation scheme to thefourth implementation scheme, and the user plane protocol stackconfiguration scheme #1 for the data reception which is based on each ofthe first implementation scheme to the fourth implementation scheme willbe described below.

Firstly, a user plane protocol stack configuration scheme #1 for a datareception which is based on the first implementation scheme will bedescribed below.

A UE receives data from one UE at a time. A UE which receives datamaintains only one radio bearer (i.e. a PDCP layer entity and a RLClayer entity) for a data reception. In this case, a user plane protocolstack includes one PDCP layer entity, one RLC layer entity, and one MAClayer entity.

The radio bearer, i.e., a PDCP layer entity and a RLC layer entity areidentified by a source identifier, i.e. a UE ID of a UE from which theUE receives the data.

An example of a structure of a user plane protocol stack for a datatransmission and reception which is based on a user plane protocol stackconfiguration scheme #1 in a connectionless communication systemaccording to an embodiment of the present disclosure will be describedwith reference to FIG. 2.

FIG. 2 schematically illustrates an example of a structure of a userplane protocol stack for a data transmission and reception which isbased on a user plane protocol stack configuration scheme #1 in aconnectionless communication system according to an embodiment of thepresent disclosure.

Referring to FIG. 2, the user plane protocol stack 200 for datatransmission includes a PDCP layer entity 201, a RLC layer entity 203and a MAC layer entity 205. The PDCP layer entity 201 and the RLC layerentity 203 are identified by a destination ID. The user plane protocolstack 210 for data reception includes a PDCP layer entity 211, a RLClayer entity 213 and a MAC layer entity 215. The PDCP layer entity 211and the RLC layer entity 213 are identified by a source identifier, i.e.a UE ID of a UE from which the UE receives the data.

A user plane protocol stack configuration scheme #1 for a data receptionwhich is based on the first implementation scheme will be describedbelow.

1) Filtering by a physical layer entity using a destination identifierin a scheduling assignment:

The physical layer entity (not shown in FIG. 2) in the UE receives thescheduling assignment and determines whether the scheduling assignmentis destined for the UE. The destination identifier field in thescheduling assignment indicates a destination ID (i.e. a group ID or abroadcast ID or a UE ID). The physical layer entity receives and decodesa physical layer packet carrying a MAC PDU, and sends the MAC PDU to aMAC layer entity if the destination identifier field in the schedulingassignment is equal to the group ID of a group of which the UE is amember or if the destination identifier field in the schedulingassignment is equal to the UE ID or if the destination identifier fieldin the scheduling assignment is equal to the broadcast ID.

Alternately, the destination identifier field in the schedulingassignment indicates a part of the destination ID (for example, the partis n LSBs or MSBs of the destination ID). The physical layer entityreceives and decodes a physical layer packet carrying a MAC PDU, andsends the MAC PDU to a MAC layer entity if the destination identifierfield in the scheduling assignment is equal to a part of the group ID ofa group of which the UE is a member or if the destination identifierfield in the scheduling assignment is equal to a part of the UE ID or ifthe destination identifier field in the scheduling assignment is equalto a part of the broadcast ID.

Filtering by the physical layer entity is performed only if thescheduling assignment with the destination ID is transmitted in thesystem.

2) Filtering by the MAC layer entity 205 using a destination identifierin a MAC PDU:

The MAC layer entity 215 in the UE receives a MAC PDU from a physicallayer entity (not shown in FIG. 2), and determines whether the MAC PDUwhich is received from the physical layer entity is destined for the UE.The destination identifier field in a MAC header of the MAC PDUindicates a destination ID (i.e. a group ID or a broadcast ID or a UEID). The received MAC PDU is destined for the UE if the destinationidentifier field is equal to the group ID of a group of which the UE isa member or if the destination identifier field is equal to the UE ID orif the destination identifier field is equal to the broadcast ID.

The destination identifier field in the MAC header of the MAC PDU mayindicate a part of the destination ID (i.e. n LSBs or n MSBs of thegroup ID or the broadcast ID or the UE ID). The received MAC PDU isdestined for the UE if the destination identifier field is equal to apart of the group ID of a group of which the UE is a member or if thedestination identifier field is equal to a part of the UE ID or if thedestination identifier field is equal to a part of the broadcast ID.Filtering by the MAC layer entity 215 is performed only if the MAC PDUwith the destination ID is transmitted in the system. If the MAC PDUwhich is received from the physical layer entity is not destined for theUE then the MAC layer entity may discard the MAC PDU.

3) Determination of a source identifier and Filtering by the MAC layerentity 215 using the source identifier:

The MAC layer entity 215 determines a UE ID of a UE which transmits theMAC PDU. For example, the operation of determining the UE ID of the UEwhich transmits the MAC PDU may be performed by reading the sourceidentifier field from a MAC header. Alternatively, the operation ofdetermining the UE ID of the UE which transmits the MAC PDU may beperformed by reading the source identifier field from schedulingassignment information. This filtering may be optional. The MAC layerentity 215 in the UE may determine whether the UE ID of a UE whichtransmits the MAC PDU is of interest to the UE. If not, then the MAClayer entity 215 discards the MAC PDU.

4) The MAC layer entity 215 in the UE determines whether there is aradio bearer (i.e. a PDCP layer entity and a RLC layer entity) for adata reception corresponding to the source identifier, i.e. the UE ID ofa UE from which UE has received the MAC PDU.

a) If a radio bearer (i.e. a PDCP layer entity and a RLC layer entity)for data reception is not already established/created then, the MAClayer entity 215 triggers creation of a new radio bearer (i.e. the PDCPlayer entity and the RLC layer entity for a data reception, andidentifies the created radio bearer (i.e. the PDCP layer entity and theRLC layer entity) for the data reception using a source identifier ofthe received MAC PDU. The MAC layer entity 215 transmits MAC servicedata units (SDUs) included in the MAC PDU to the RLC layer entity 213corresponding to the new radio bearer. The PDCP layer entity 211 and theRLC layer entity 213 are configured using default (or pre-configured)values.

b) If a radio bearer (i.e. a PDCP layer entity and a RLC layer entity)is already established/created for the data reception, and if the sourceidentifier of the received MAC PDU is different from a source identifierof existing radio bearer for a data reception, the MAC layer entity 215triggers release of the existing radio bearer (i.e. the PDCP layerentity and the RLC layer entity) and establishment of a radio bearer(i.e. the PDCP layer entity and the RLC layer entity), and identifiesthe the radio bearer (i.e. the PDCP layer entity and the RLC layerentity) using a source identifier included in the received MAC PDU.

Alternatively, if the radio bearer (i.e. the PDCP layer entity and theRLC layer entity) for the data reception is already established/created,and if the source identifier of the received MAC PDU is different fromthe source identifier of the existing radio bearer for the datareception, and has preference higher than preference of the sourceidentifier of the existing radio bearer (i.e. the PDCP layer entity andthe RLC layer entity) for the data reception, the MAC layer entity 215triggers release of the existing radio bearer (i.e. the PDCP layerentity and the RLC layer entity) for the data reception andestablishment of the new radio bearer (i.e. a PDCP layer entity and aRLC layer entity) for the data reception, and identifies the new radiobearer (i.e. the PDCP layer entity and the RLC layer entity) for thedata reception using the source identifier included in the received MACPDU.

Alternatively, if the radio bearer (i.e. the PDCP layer entity and theRLC layer entity) for the data reception exists, and if the sourceidentifier of the received MAC PDU is different from the sourceidentifier of the existing radio bearer (i.e. the PDCP layer entity andthe RLC layer entity) for the data reception, and a service for a newsource identifier has preference higher than preference of a service fora current source identifier, the MAC layer entity 215 triggers releaseof the old radio bearer (i.e. the PDCP layer entity and the RLC layerentity) for the data reception, and establishment of a new radio bearer(i.e. a PDCP layer entity and a RLC layer entity) for a data reception,and identifies the new radio bearer (i.e. the PDCP layer entity and theRLC layer entity) for the data reception using the source identifier ofthe received MAC PDU.

Here, a service indicator may be included in the MAC PDU, or a servicepriority may be included in the MAC PDU. For example, the serviceindicator indicates a service type of a related service, and mayindicate that the related service is a voice service or a data service.The MAC layer entity 215 transmits the MAC SDU(s) included in the MACPDU to the RLC layer entity 213 corresponding to the new radio bearer.

c) If the radio bearer (i.e. the PDCP layer entity and the RLC layerentity) are already established for the data reception, and if thesource identifier of the received MAC PDU is identical to a sourceidentifier of already established radio bearer for a data reception, theMAC layer entity 215 transmits the MAC SDUs included in the MAC PDU tothe RLC layer entity corresponding to the radio bearer.

Meanwhile, if there is no activity for a pre-defined time period, aradio bearer (i.e. a PDCP layer entity and a RLC layer entity) for thedata reception are released. The established radio bearer (i.e. the PDCPlayer entity and the RLC layer entity) for the data reception arereleased if the upper layer entity indicates to stop monitoring D2Dcommunication.

A user plane protocol stack configuration scheme #1 for a data receptionwhich is based on the first implementation scheme has been describedabove, and a user plane protocol stack configuration scheme #1 for adata reception which is based on the second implementation scheme willbe described below.

A UE receives data from one UE at a time. The UE which receives the datamaintains only one radio bearer (i.e. a PDCP layer entity and a RLClayer entity) for a data reception.

The user plane protocol stack includes one PDCP layer entity, one RLClayer entity, and one MAC layer entity. The radio bearer, i.e., a PDCPlayer entity and a RLC layer entity are identified by a sourceidentifier, i.e. UE ID of a UE from which the UE receives data. Astructure of the user plane protocol stack is identical to a structureof a user plane protocol stack illustrated in FIG. 2.

The UE establishes a default radio bearer (i.e. a PDCP layer entity anda RLC layer entity) using default configuration when the upper layerentity triggers to monitor D2D communication. The established defaultradio bearer (i.e. the PDCP layer entity and the RLC layer entity) isnot associated with a source identifier, and a source identifiercorresponding to the established default radio bearer (i.e. the PDCPlayer entity and the RLC layer entity) is null. For convenience, asource identifier which is null is called a null source identifier.

An operating process of a UE in the user plane protocol stackconfiguration scheme #1 for the data reception which is based on thesecond implementation scheme will be described below.

1) Filtering by Physical layer entity using destination identifier inscheduling assignment:

The physical layer entity in the UE receives the scheduling assignmentand determines whether the scheduling assignment is destined for the UE.The destination identifier field in scheduling assignment informationindicates destination ID (i.e. group ID or broadcast ID or UE ID). Thephysical layer entity receives, decodes the physical layer packetcarrying MAC PDU and sends the MAC PDU to MAC layer entity if thedestination identifier field in the scheduling assignment is equal togroup ID of group of which the UE is a member or if the destinationidentifier field in the scheduling assignment is equal to UE ID or ifthe destination identifier field in the scheduling assignment is equalto broadcast ID.

Alternately, the destination identifier field in scheduling assignmentinformation indicates part of destination ID (for example part is n LSBsor MSBs of destination ID). The physical layer entity receives, decodesthe physical layer packet carrying MAC PDU and sends the MAC PDU to MAClayer entity if the destination identifier field in the schedulingassignment is equal to part of group ID of group of which the UE is amember or if the destination identifier field in the schedulingassignment is equal to part of UE ID or if the destination identifierfield in the scheduling assignment is equal to part of broadcast ID.

Filtering by physical layer entity is performed only if schedulingassignment with destination ID is transmitted in the system.

2) Filtering by MAC layer entity using destination identifier in MACPDU:

The MAC layer entity 215 in the UE receives a MAC PDU from a physicallayer entity, and determines whether the MAC PDU is destined for the UE.The destination identifier field in MAC header of MAC PDU indicatesdestination ID (i.e. group ID or broadcast ID or UE ID). The receivedMAC PDU is destined for the UE if the destination identifier field isequal to group ID of group of which the UE is a member or if thedestination identifier field is equal to UE ID or if the destinationidentifier field is equal to broadcast ID. The destination identifierfield in MAC header of MAC PDU indicates part of destination ID (i.e. nLSBs or n MSBs of group ID or broadcast ID or UE ID). The received MACPDU is destined for the UE if the destination identifier field is equalto part of group ID of group of which the UE is a member or if thedestination identifier field is equal to part of UE ID or if thedestination identifier field is equal to part of broadcast ID. Filteringby MAC layer entity is performed only if MAC PDU with destination ID istransmitted in the system.

3) Determination of a source identifier and Filtering by MAC layerentity using source identifier:

The MAC layer entity 215 determines a UE ID of a UE which transmits theMAC PDU. For example, the UE ID of the UE which transmits the MAC PDUmay be determined by reading the source identifier field from a MACheader. Alternatively, the UE ID of the UE which transmits the MAC PDUmay be determined by reading the source identifier field from schedulingassignment information. This filtering is optional. The MAC layer entity215 in the UE may determine whether the UE ID of a UE which transmitsthe MAC PDU is of interest to the UE. If not, then the MAC layer entity215 discards the MAC PDU.

4) The MAC layer entity 215 determines whether there is a radio bearer(i.e. a PDCP layer entity and a RLC layer entity) for a data receptioncorresponding to the source identifier, i.e. a UE ID of a UE from whicha UE has received the MAC PDU.

a) If there is no radio bearer (i.e. a PDCP layer entity and a RLC layerentity) which is already established for a data reception except thedefault radio bearer, the MAC layer entity 215 uses the default radiobearer. The null source identifier for the default radio bearer ischanged to the source identifier of the received MAC PDU, so the defaultradio bearer becomes a non default radio bearer. The MAC layer entity215 transmits the MAC SDU(s) included in the MAC PDU to the RLC layerentity 213 corresponding to the non default radio bearer.

b) If the non default radio bearer, i.e., a radio bearer which is notassociated with the null source identifier is already established for adata reception, and if the source identifier of the received MAC PDU isdifferent from a source identifier of existing radio bearer for a datareception, the MAC layer entity 215 triggers release of the existingradio bearer, and establishment of a new radio bearer, and identifiesthe establishment of the new radio bearer using the source identifierincluded in the received MAC PDU.

Alternatively, if the non default radio bearer for the data reception isalready established, and if the source identifier of the received MACPDU is different from the source identifier of an existing radio bearerfor a data reception, and has preference higher than preference of thesource identifier of the existing radio bearer/for the data reception,the MAC layer entity 215 triggers release of the existing radio bearerfor the data reception and establishment of a new radio bearer for adata reception, and identifies the new radio bearer for the datareception using the source identifier of the received MAC PDU.

Alternatively, if the non default radio bearer for the data reception isalready established, and if the source identifier of the received MACPDU is different from the source identifier of the existing radio bearerfor the data reception, and has preference higher than preference of thesource identifier of the existing radio bearer for the data reception,the MAC layer entity 215 triggers release of the existing radio bearerfor the data reception, and establishment of a new radio bearer for datareception, and identifies the new radio bearer for the data receptionusing the source identifier of the received MAC PDU.

Here, a service indicator may be included in the MAC PDU, or a servicepriority may be included in the MAC PDU. For example, the serviceindicator indicates whether a related service is a voice service or adata service. The MAC layer entity 215 transmits the MAC SDU(s) includedin the MAC PDU to the RLC layer entity 213 corresponding to the newradio bearer.

c) If a non default radio bearer is already established for a datareception, and if the source identifier of the received MAC PDU isidentical to a source identifier of an existing radio bearer for a datareception, the MAC layer entity 215 transmits the MAC SDUs included inthe MAC PDU to the RLC layer entity 213 corresponding to a related radiobearer.

Meanwhile, if there is no activity for a pre-defined time period, thenon default radio bearer for the data reception are released, and adefault radio bearer is established with default configuration. Theestablished default and non default radio bearer for the data receptionare released if the upper layer entity indicates to stop monitoring D2Dcommunication.

A user plane protocol stack configuration scheme #1 for a data receptionwhich is based on the second implementation scheme has been describedabove, and a user plane protocol stack configuration scheme #1 for adata reception which is based on the third implementation scheme will bedescribed below.

A UE may receive data from a plurality of UEs concurrently. The UE whichreceives the data maintains one or more radio bearers (i.e. PDCP layerentities and RLC layer entities) for a data reception. Here, each radiobearer (i.e. a PDCP layer entity and a RLC layer entity) is forreceiving data from a different UE. The user plane protocol stackincludes one PDCP layer entity, one RLC layer entity per radio bearer,and one MAC layer entity. The radio bearer, i.e., a PDCP layer entityand a RLC layer entity are identified by a UE ID of a UE from which theUE receives the data.

Another example of a structure of a user plane protocol stack for a datatransmission and reception which is based on a user plane protocol stackconfiguration scheme #1 in a connectionless communication systemaccording to an embodiment of the present disclosure will be describedwith reference to FIG. 3.

FIG. 3 schematically illustrates another example of a structure of auser plane protocol stack for data transmission and reception which isbased on a user plane protocol stack configuration scheme #1 in aconnectionless communication system according to an embodiment of thepresent disclosure.

Referring to FIG. 3, it will be noted that a user plane protocol stack310 in FIG. 3 is a user plane protocol stack including a plurality of RXradio bearers, i.e. plurality of PDCP layer entities 311 and a pluralityof RLC layer entities 313.

The user plane protocol stack 300 for data transmission includes a PDCPlayer entity 301, a RLC layer entity 303 and a MAC layer entity 305. ThePDCP layer entity 301 and the RLC layer entity 303 are identified by adestination ID.

The user plane protocol stack 310 for data reception includes a PDCPlayer entity #1 311-1 and a RLC layer entity #1 313-1 corresponding to afirst radio bearer #1, includes a PDCP layer entity #2 311-2 and a RLClayer entity #2 313-2 corresponding to a second radio bearer #2, and soon. The user plane protocol stack 310 for data reception also includes aMAC layer entity 315 which is common across all of the radio bearers.The PDCP layer entities 311 and the RLC layer entities 313 areidentified by a source identifier.

A user plane protocol stack configuration scheme #1 for a data receptionwhich is based on the third implementation scheme will be describedbelow.

1) Filtering by a physical layer entity using a destination identifierin a scheduling assignment:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

2) Filtering by the MAC layer entity 315 using a destination identifierin a MAC PDU:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

3) Determination of a source identifier and Filtering by the MAC layerentity 315 using a source identifier:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

4) The MAC layer entity 315 in the UE determines whether there is aradio bearer (i.e. a PDCP layer entity and a RLC layer entity) for adata reception corresponding to the source identifier, i.e. a UE ID of aUE from which UE has received the MAC PDU.

a) If a radio bearer (i.e. a PDCP layer entity and a RLC layer entity)for data reception is not already established or created then, the MAClayer entity 315 triggers creation of a new radio bearer (i.e. a PDCPlayer entity and a RLC layer entity), and identifies the new radiobearer (i.e. the PDCP layer entity and the RLC layer entity) for thedata reception using a source identifier of the received MAC PDU. TheMAC layer entity 315 transmits MAC SDUs included in the MAC PDU to theRLC layer entity 313 corresponding to the new radio bearer. If the newradio bearer is established, the PDCP layer entity 311 and the RLC layerentity 313 are configured using default (or pre-configured) values.

b) If a radio bearer (i.e. a PDCP layer entity and a RLC layer entity)is already established, and if the source identifier of the received MACPDU is different from a source identifier of an existing radio bearer(i.e. a PDCP layer entity and a RLC layer entity), the MAC layer entity315 triggers establishment of a new radio bearer (i.e. a PDCP layerentity and a RLC layer entity), and identifies the new radio bearer(i.e. the PDCP layer entity and the RLC layer entity) using a sourceidentifier of the received MAC PDU. The MAC layer entity 315 transmitsthe MAC SDU(s) included in the MAC PDU to the RLC layer entity 313corresponding to the new radio bearer.

c) If a radio bearer (i.e. a PDCP layer entity and a RLC layer entity)is already established, and if the source identifier of the received MACPDU is identical to the source identifier of the existing radio bearer(i.e. a PDCP layer entity and a RLC layer entity), the MAC layer entity315 transmits the MAC SDU(s) included in the MAC PDU to the RLC layerentity 313 corresponding to a related radio bearer.

If there is no activity for a pre-defined time period, the radio bearerfor the data reception is released.

Meanwhile, if a voice service is received from one TX UE, the MAC layerentity 315 may not establish a radio bearer with another TX UE for avoice service. Alternatively, the MAC layer entity 315 may release anold voice service, and generate a new radio bearer for a voice servicewith a new TX UE. Here, the new radio bearer (i.e. a PDCP layer entityand a RLC layer entity) may be generated based on TX UE preference. TheMAC layer entity 315 may identify a voice service using some indicatorin a MAC PDU. Alternatively, maintenance for one voice service may beprocessed in a upper layer entity. If the voice service is received fromone TX UE, voice packets from another TX UE may be discarded by theupper layer entity.

A user plane protocol stack configuration scheme #1 for a data receptionwhich is based on the third implementation scheme has been describedabove, and a user plane protocol stack configuration scheme #1 for adata reception which is based on the fourth implementation scheme willbe described below.

A UE may receive data from a plurality of UEs concurrently. The UE whichreceives the data maintains one or more radio bearers (i.e. PDCP layerentities and RLC layer entities) for a data reception. Here, each radiobearer is for receiving data from a different UE. In this case, the userplane protocol stack includes one PDCP layer entity, one RLC layerentity per radio bearer, and one MAC layer entity. The radio bearer,i.e., a PDCP layer entity and a RLC layer entity are identified by asource identifier, i.e. UE ID of a UE from which the UE receives thedata. Here, the user plane protocol stack is identical to a user planeprotocol stack illustrated in FIG. 3, so a detailed description will beomitted herein.

A UE establishes a default radio bearer (i.e. a PDCP layer entity and aRLC layer entity) using default configuration if a upper layer entitytriggers to monitor D2D communication. The established default radiobearer (i.e. the PDCP layer entity and the RLC layer entity) is notassociated with a source identifier, and a source identifiercorresponding to the established default radio bearer is null.

An operating process of a UE in the user plane protocol stackconfiguration scheme #1 for the data reception which is based on thefourth implementation scheme will be described below.

1) Filtering by a physical layer entity using a destination identifierin a scheduling assignment:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

2) Filtering by a MAC layer entity using a destination identifier in aMAC PDU:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

3) Determination of a source identifier and Filtering by a MAC layerentity using a source identifier:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

4) The MAC layer entity 315 determines whether there is a radio bearer(i.e. a PDCP layer entity and a RLC layer entity) for a data receptioncorresponding to the source identifier, i.e. a UE ID of a UE from whicha UE has received the MAC PDU.

a) If there is no radio bearer (i.e. a PDCP layer entity and a RLC layerentity) which is already established other than the default radiobearer, the MAC layer entity 315 uses the default radio bearer. The nullsource identifier of the default radio bearer is changed to a sourceidentifier received in the MAC PDU. The MAC layer entity 315 transmitsthe MAC SDU(s) included in the MAC PDU to the RLC layer entity 313corresponding to the radio bearer. The MAC layer entity 315 triggersgeneration of a new default radio bearer.

b) If a non default radio bearer is already established, and if thesource identifier of the received MAC PDU is different from a sourceidentifier of an existing radio bearer, the MAC layer entity 315 usesthe default radio bearer. The null source identifier of the defaultradio bearer is changed to the source identifier received through theMAC PDU. The MAC layer entity 315 transmits the MAC SDU(s) included inthe received MAC PDU to the RLC layer entity 313 corresponding to theradio bearer. The MAC layer entity 315 triggers generation of a newdefault radio bearer.

c) If a non default radio bearer is already established, and if thesource identifier of the received MAC PDU is identical to a sourceidentifier of an existing radio bearer, the MAC layer entity 315transmits the MAC SDU(s) included in the MAC PDU to RLC layer entitycorresponding to this radio bearer.

If there is no activity for a pre-defined time period, the radio bearerfor the data reception is released. The default radio bearer and the nondefault radio bearer which are established for the data reception arereleased if the upper layer entity indicates to stop monitoring D2Dcommunication.

In this embodiment, if a voice service is received from one TX UE, theMAC layer entity 315 may not establish a radio bearer with another TX UEfor a voice service. Alternatively, the MAC layer entity 315 may releasean old voice service, and generate a new radio bearer for a voiceservice with a new TX UE. Here, the new radio bearer may be generatedbased on TX UE preference. The MAC layer entity 315 may identify a voiceservice using some indicator in a MAC PDU. Alternatively, maintenancefor one voice service may be processed in a upper layer entity. If thevoice service is received from one TX UE, voice packets from another TXUE may be discarded by the upper layer entity.

As described above, in a user plane protocol stack configuration scheme#1 for a data reception which is based on each of the firstimplementation scheme to the fourth implementation scheme, a MAC layerentity may indicate a RRC layer entity to create/release a radio bearer(i.e. a PDCP layer entity and a RLC layer entity), or may create/releasea new radio bearer (i.e. a PDCP layer entity and a RLC layer entity).

A user plane protocol stack configuration scheme #1 has been describedabove, and a user plane protocol stack configuration scheme #2 will bedescribed below.

A user plane protocol stack configuration scheme #2 for a datatransmission in a D2D communication system will be described below.

A UE which transmit data to one or more UEs maintains a plurality ofradio bearers for D2D data transmission. Each radio bearer refers to aset of one PDCP layer entity and one RLC layer entity. Here, one radiobearer is for one destination. For example, radio bearers for broadcast,unicast and group cast may be different. For the group cast, a radiobearer for a different group is different. Similarly, for the unicast, aradio bearer for different UEs is different. The radio bearer is mappedto one logical channel, and the logical channel is mapped to a D2Dcommunication transport channel which is mapped to a D2D communicationbroadcast physical channel.

In the UE, a radio bearer (i.e. a PDCP layer entity and a RLC layerentity) for a data transmission is created/established if a upper layerentity triggers a data transmission. The upper layer entity may be aProSe Protocol entity or a Application Protocol entity. Further, a PDCPlayer entity and a RLC layer entity are created/established andconfigured using default values.

The upper layer entity may indicate whether the data transmission in theUE is a broadcast transmission, a unicast transmission, or a group casttransmission. That is, the upper layer entity may indicate the datatransmission in the UE is the broadcast transmission, the unicasttransmission, or the group cast transmission by transmitting informationwhich indicates that the data transmission in the UE is the broadcasttransmission, the unicast transmission, or the group cast transmission.If the data transmission is the unicast transmission then upper layerentity provides the destination UE ID. If the data transmission is thegroupcast transmission, then upper layer provides the destination GroupID The UE ID of the UE may also be provided by the upper layer entity.

The created/estsblished radio bearer (i.e the PDCP layer entity and theRLC layer entity) is removed if the upper layer entity stops the datatransmission corresponding to the destination associated with that radiobearer. The generated radio bearer (i.e. the PDCP layer entity and theRLC layer entity) may be removed by the RRC layer entity of the MAClayer entity in one system.

A priority may be assigned to a radio bearer based on a destination (forexample, unicast may have a priority higher than a priority ofbroadcast) or a type of a service (for example, a voice service may havea priority higher than a priority of a data service). In the UE, a radiobearer established for a data transmission is released if the upperlayer triggers to release the radio bearer established for the datatransmission.

The radio bearers (i.e PDCP layer entities and RLC layer entities) maybe identified as one of an option A and an option B.

(1) Option A: destination ID (a group ID, a unicast ID (i.e. a UE ID),or a broadcast ID) based

(2) Option B: LCID based. An LCID is local to a transmitting UE, andassignment of an LCID for a radio bearer is maintained by thetransmitting UE. If the LCID is used to identify radio bearers for adata transmission, the UE includes the LCID into a MAC header of the MACPDU.

During the data transmission the PDCP layer entity processes (i.e.applies security and/or header compression and/or sequence numbering tothe packets) the packets received from upper layer and sends to the RLClayer entity. The RLC layer entity processes (applies sequence numberingand/or fragmentation) these packets (i.e. RLC SDUs) and sends them tothe MAC layer entity. The MAC layer entity transmits one or more ofthese packets (i.e. MAC SDUs) corresponding to the same destination IDin the MAC PDU.

During the data transmission, a source identifier and a destinationidentifier are transmitted by the UE and the scheme of transmitting themis same as described in the user plane protocol stack configurationscheme #1, so a detailed description will be omitted herein.

A user plane protocol stack configuration scheme #2 for a datatransmission has been described above, and a user plane protocol stackconfiguration scheme #2 for a data reception will be described below.

The user plane protocol stack configuration scheme #2 for the datareception is based on one of the first implementation scheme to thefourth implementation scheme, and the user plane protocol stackconfiguration scheme #2 for the data reception which is based on each ofthe first implementation scheme to the fourth implementation scheme willbe described below.

Firstly, a user plane protocol stack configuration scheme #2 for a datareception which is based on the first implementation scheme will bedescribed below.

A UE receives data from one TX UE at a time. The UE maintains one ormore radio bearers for a data reception. Each of the radio bearersexists for a data reception from the same UE. A user plane protocolstack includes one PDCP layer entity per radio bearer, one RLC layerentity per radio bearer, and one MAC layer entity. The radio bearer,i.e., a PDCP layer entity and a RLC layer entity are identified by apair of a source identifier i.e. UE ID of a UE from which UE receivesdata and a destination ID or LCID, i.e., a <TX UE ID, destination ID orLCID>.

An example of a structure of a user plane protocol stack for datatransmission and reception which is based on a user plane protocol stackconfiguration scheme #2 in a connectionless communication systemaccording to an embodiment of the present disclosure will be describedwith reference to FIG. 4.

FIG. 4 schematically illustrates an example of a structure of a userplane protocol stack for a data transmission and reception which isbased on a user plane protocol stack configuration scheme #2 in aconnectionless communication system according to an embodiment of thepresent disclosure.

Referring to FIG. 4, it will be noted that a user plane protocol stack400 in FIG. 4 is a user plane protocol stack for data transmissionincluding a plurality of TX radio bearers, i.e. a plurality of PDCPlayer entities 401 and a plurality of RLC layer entities 403, and a userplane protocol stack 410 in FIG. 4 is a user plane protocol stack fordata reception including a plurality of RX radio bearers, i.e. aplurality of PDCP layer entities 411 and a plurality of RLC layerentities 413.

The user plane protocol stack 400 for data transmission includes a PDCPlayer entity #1 401-1 and a RLC layer entity #1 403-1 corresponding to afirst radio bearer #1, includes a PDCP layer entity #2 401-2 and a RLClayer entity #2 403-2 corresponding to a second radio bearer #2, and soon. The user plane protocol stack 400 for data transmission alsoincludes a MAC layer entity 405 which is common across all of the radiobearers. The PDCP layer entity 401 and the RLC layer entity 403 areidentified by a destination ID or a LCID.

The user plane protocol stack 410 for data reception includes a PDCPlayer entity #1 411-1 and a RLC layer entity #1 413-1 corresponding to afirst radio bearer #1, includes a PDCP layer entity #2 411-2 and a RLClayer entity #2 413-2 corresponding to a second radio bearer #2, and soon. The user plane protocol stack 410 for data reception also includes aMAC layer entity 415 which is common across all of the radio bearers.The PDCP layer entity 411 and RLC layer entity 413 are identified by asource identifier and one of a destination ID or a LCID. The user planeprotocol stack configuration scheme #2 for the data reception which isbased on the first implementation scheme will be described below.

1) Filtering by a physical layer entity using destination identifier ina scheduling assignment:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein. The destination identifieris transmitted to the MAC layer entity 415 along with MAC PDU.

2) Filtering by the MAC layer entity 415 using a destination identifierin a MAC PDU:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

3) Determination of a source identifier and Filtering by the MAC layerentity 415 using a source identifier:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

4) The MAC layer entity 415 in the UE determines a destination ID or anLCID of the MAC SDU(s) in the received MAC PDU. The destination ID orthe LCID may be determined by reading the destination ID or the LCIDfrom a MAC header of the MAC PDU. In case one part of the destination IDis transmitted in a destination identifier field in the MAC header ofthe MAC PDU and another part of the destination ID is transmitted inscheduling assignment information, the MAC layer entity 415 determinesthe destination ID by combining both of the parts of the destination ID.

5) For each MAC SDU received in the MAC PDU, the MAC layer entity 415 inthe UE determines whether there is a radio bearer (i.e. a PDCP layerentity and a RLC layer entity) for a data reception.

a) If there is no radio bearer (i.e. a PDCP layer entity and a RLC layerentity) which is already established for a data reception, the MAC layerentity 415 triggers a creation/establishment of a new radio bearer (i.e.a PDCP layer entity and a RLC layer entity), and identifies the newradio bearer (i.e. the PDCP layer entity and the RLC layer entity) forthe data reception using a <source identifier, destination ID/LCID> ofthe MAC SDU received in the MAC PDU. The MAC layer entity 415 transmitsthe MAC SDU to the RLC layer entity 413 corresponding to the new radiobearer. If the new radio bearer (i.e. the PDCP layer entity and the RLClayer entity) is established, the PDCP layer entity 411 and the RLClayer entity 413 are configured using default (or pre-configured)values.

b) If a radio bearer (i.e. a PDCP layer entity and a RLC layer entity)is already established, and if the source identifier of the MAC SDUreceived in the MAC PDU is different from source identifiers of existingradio bearers (i.e. PDCP layer entities and RLC layer entities), the MAClayer entity 415 triggers release of the existing radio bearers, andestablishment of a new radio bearer, and identifies the new radio bearerusing the <source identifier, destination ID/LCID> of the MAC SDU. TheMAC layer entity 415 transmits the MAC SDU to the RLC layer entity 413corresponding to the new radio bearer.

c) If a radio bearer is already established, and if the sourceidentifier of the MAC SDU received in the MAC PDU is identical to asource identifier of an existing radio bearer, and a destination ID oran LCID of the MAC SDU is identical to a destination ID or an LCID ofthe existing radio bearer, the MAC layer entity 415 transmits the MACSDU to the RLC layer entity 413 corresponding to the existing radiobearer.

d) If a radio bearer is already established, and if the sourceidentifier of the MAC SDU received in the MAC PDU is identical to thesource identifier of the existing radio bearer, and a destination ID oran LCID of the MAC PDU is different from a destination ID or an LCID ofthe existing radio bearer, the MAC layer entity 415 triggersestablishment of a new radio bearer, and transmits the MAC SDU to theRLC layer entity 413 corresponding to the new radio bearer.

If there is no activity for a pre-defined time period, the radio bearerfor the data reception is released. The established radio bearer for thedata reception is released if the upper layer entity indicates to stopmonitoring D2D communication.

A user plane protocol stack configuration scheme #2 for a data receptionwhich is based on the first implementation scheme has been describedabove, and a user plane protocol stack configuration scheme #2 for adata reception which is based on the second implementation scheme willbe described below.

A UE receives data from one TX UE at a time. The UE maintains one ormore radio bearers for a data reception. Here, each radio bearer is fora data reception from the same UE. A user plane protocol stack includesone PDCP layer entity, one RLC layer entity per radio bearer, and oneMAC layer entity. The radio bearer, i.e., the PDCP layer entity and theRLC layer entity are identified by a <source identifier, i.e. UE ID of aUE from which the UE receives the data, destination ID/LCID>. Here, theuser plane protocol stack is identical to a user plane protocol stackillustrated in FIG. 4, so a detailed description will be omitted herein.

In this case, a UE establishes a default radio bearer using defaultconfiguration if the upper layer entity triggers to monitor D2Dcommunication. The established default radio bearer is identified by a<Source Identifier=null, destination ID/LCID=null>. The UE may alsoestablish a plurality of default radio bearers, one for broadcast, onefor unicast and one or more for associated groups of the UE.

An operating process of a UE in a user plane protocol stackconfiguration scheme #2 for a data reception which is based on thesecond implementation scheme will be described below.

1) Filtering by a physical layer entity using a destination identifierin a scheduling assignment:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein. The destination identifieris transmitted to the MAC layer entity 415 along with the MAC PDU.

2) Filtering by the MAC layer entity 415 using a destination identifierin a MAC PDU:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

3) Determination of a source identifier and Filtering by the MAC layerentity 415 using a source identifier:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

4) The MAC layer entity 415 in the UE determines a destination ID or anLCID of MAC SDU(s) received in the MAC PDU. The destination ID or theLCID may be determined by reading the destination ID or the LCID from aMAC header of the MAC PDU. In case one part of the destination ID istransmitted in a destination identifier field in the MAC header of theMAC PDU and another part of the destination ID is transmitted inscheduling assignment information, the MAC layer entity 415 determinesthe destination ID by combining both of the parts of the destination ID.

5) For each MAC SDU received in the MAC PDU, the MAC layer entity 415 inthe UE determines whether there is a radio bearer (i.e. a PDCP layerentity and a RLC layer entity) for a data reception.

a) If there is no radio bearer (i.e. a PDCP layer entity and a RLC layerentity) which is already established for a data reception except defaultradio bearer(s), the MAC layer entity 415 uses the default radio beareror a default radio bearer corresponding to the destination ID. The<source identifier=null, destination ID/LCID=null> is changed to a<source identifier, destination ID/LCID> corresponding to the MAC SDUreceived in the MAC PDU, so the radio bearer becomes a non default radiobearer. The MAC layer entity 415 transmits the MAC SDU to the RLC layerentity 413 corresponding to the radio bearer. The MAC layer entity 415triggers generation of a new default radio bearer.

b) If a non default radio bearer is already established, and if thesource identifier of the MAC SDU is different from a source identifierof each of the existing radio bearers, the MAC layer entity 415 triggersrelease of the existing radio bearers, and establishment of a new radiobearer, and identifies the new radio bearer using the <sourceidentifier, destination ID/LCID> of the MAC SDU. The MAC layer entity415 transmits the MAC SDU to the RLC layer entity 413 corresponding tothe new radio bearer.

c) If non default radio bearer is already established, and if the sourceidentifier included in the MAC SDU is identical to the source identifierof the existing radio bearer, and a destination ID or an LCID of the MACSDU is identical to a destination ID or an LCID of the existing radiobearer, the MAC layer entity 415 transmits the MAC SDU to the RLC layerentity 413 corresponding to the existing radio bearer.

d) If a non default radio bearer are already established, and if thesource identifier of the MAC SDU received in the MAC PDU is identical tothe source identifier of the existing radio bearer, and a destination IDor an LCID of the MAC SDU is different from the destination ID or theLCID of the existing radio bearer, the MAC layer entity 415 uses thedefault radio bearer or a default radio bearer corresponding to thedestination ID. The <source identifier=null, destination ID/LCID=null>is changed to the <source identifier, destination ID/LCID> correspondingto the MAC SDU, so the radio bearer becomes a non default radio bearer.The MAC layer entity 415 transmits the MAC SDU to the RLC layer entity413 corresponding to the radio bearer. The MAC layer entity 415 alsotriggers generation of a new default radio bearer.

If there is no activity for a pre-defined time period, the radio bearerfor the data reception is released. The established default or nondefault radio bearer for the data reception is released if the upperlayer entity indicates to stop monitoring D2D communication.

A user plane protocol stack configuration scheme #2 for a data receptionwhich is based on the second implementation scheme has been describedabove, and a user plane protocol stack configuration scheme #2 for adata reception which is based on the third implementation scheme will bedescribed below.

A UE may receive data from a plurality of TX UEs concurrently. The UEmaintains one or more radio bearers for a data reception. Each radiobearer is for a data reception from a different <source identifier,destination ID/LCID>.

Another example of a structure of a user plane protocol stack for a datareception which is based on a user plane protocol stack configurationscheme #2 in a connectionless communication system according to anembodiment of the present disclosure will be described with reference toFIGS. 5A and 5B.

FIGS. 5A and 5B schematically illustrate another example of a structureof a user plane protocol stack for data transmission and reception whichis based on a user plane protocol stack configuration scheme #2 in aconnectionless communication system according to an embodiment of thepresent disclosure.

FIG. 5A is a user plane protocol stack 500 for data transmissionincluding a plurality of TX radio bearers, i.e. a plurality of PDCPlayer entities 501 and a plurality of RLC layer entities 503, and a userplane protocol stack 510 in FIG. 5B is a user plane protocol stack fordata reception including a plurality of RX radio bearers, i.e. aplurality of PDCP layer entities 511 and a plurality of RLC layerentities 513.

The user plane protocol stack 500 for data transmission includes a PDCPlayer entity #1 501-1 and a RLC layer entity #1 503-1 corresponding to afirst radio bearer #1, includes PDCP layer entity #n 501-n and a RLClayer entity #2 503-n corresponding to a n-th radio bearer #n, and soon. The user plane protocol stack 500 for data transmission alsoincludes a MAC layer entity 505 which is common across all of the radiobearers. The PDCP layer entity 501 and the RLC layer entity 503 areidentified by a destination ID or a LCID.

The user plane protocol stack 510 for data reception includes a PDCPlayer entity #1 511-1 and a RLC layer entity #1 513-1 corresponding to afirst radio bearer #1, includes a PDCP layer entity #2 511-2 and a RLClayer entity #2 513-2 corresponding to a second radio bearer #2, and soon. The user plane protocol stack 510 for data reception also includes aMAC layer entity 515 which is common across all of the radio bearers.Each of the PDCP layer entities 511 and the RLC layer entities 513 areidentified by a source identifier and one of a destination ID and aLCID.

An operating process of a UE in a user plane protocol stackconfiguration scheme #2 for a data reception which is based on the thirdimplementation scheme will be described below.

1) Filtering by a physical layer entity using destination identifier ina scheduling assignment:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein. The destination identifieris transmitted to the MAC layer entity 515 along with MAC PDU.

2) Filtering by the MAC layer entity 515 using a destination identifierin a MAC PDU:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

3) Determination of a source identifier and Filtering by the MAC layerentity 515 using a source identifier:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

4) The MAC layer entity 515 determines a destination ID or an LCID ofone or more MAC SDUs received in the MAC PDU. The destination ID or theLCID may be determined by reading the destination ID or the LCID from aMAC header of the MAC PDU. In case one part of the destination ID istransmitted in a destination identifier field in the MAC header of theMAC PDU and another part of the destination ID is transmitted inscheduling assignment information, the MAC layer entity 515 determinesthe destination ID by combining both of the parts of the destination ID.

5) For each MAC SDU(s) received in the MAC PDU, the MAC layer entity 515in the UE determines whether there is a radio bearer (i.e. a PDCP layerentity and a RLC layer entity) for a data reception.

a) If there is no radio bearer (i.e. a PDCP layer entity and a RLC layerentity) which is already established for a data reception, the MAC layerentity 515 triggers a creation/establishment of a new radio bearer (i.e.a PDCP layer entity and a RLC layer entity), and identifies the newradio bearer for the data reception using a <source identifier,destination ID/LCID> of the MAC SDU received in the MAC PDU. The MAClayer entity 515 transmits the MAC SDU to the RLC layer entity 513corresponding to the new radio bearer. If the new radio bearer isestablished, the PDCP layer entities 511 and the RLC layer entities 513are configured using default (or pre-configured) values.

b) If a radio bearer (i.e. a PDCP layer entity and a RLC layer entity)is already established, and if the <source identifier, destinationID/LCID> of the MAC SDU received in the MAC PDU is different from a<source identifier, destination ID/LCID> of each of existing radiobearers, the MAC layer entity 515 triggers establishment of a new radiobearer, and identifies the new radio bearer using the <sourceidentifier, destination ID or LCID> of the MAC SDU. The MAC layer entity515 transmits the MAC SDU to the RLC layer entity 513 corresponding tothe new radio bearer.

c) If a radio bearer is already established, and if the <sourceidentifier, destination ID/LCID> included in the MAC SDU received in theMAC PDU is identical to a <source identifier, destination ID/LCID> of anexisting radio bearer, the MAC layer entity 515 transmits the MAC SDU tothe RLC layer entity 513 corresponding to the existing radio bearer.

If there is no activity for a pre-defined time period, the radio beareris released. The established radio bearer for the data reception isreleased if the upper layer entity indicates to stop monitoring D2Dcommunication.

Meanwhile, if voice service data is received from one TX UE, the MAClayer entity 515 may not establish a radio bearer/logical channel withanother TX UE for a voice service. Alternatively, the UE may release anold voice service, and generate a radio bearer for a voice service witha new TX UE. Here, the radio bearer with the new TX UE may be generatedbased on TX UE preference. The UE may identify a voice service usingsome indicator included in a MAC PDU.

Alternatively, maintenance for a voice service may be processed in theupper layer entity. If the voice service is received from one TX UE,voice service packets from another TX UE may be discarded by the upperlayer entity.

A user plane protocol stack configuration scheme #2 for a data receptionwhich is based on the third implementation scheme has been describedabove, and a user plane protocol stack configuration scheme #2 for adata reception which is based on the fourth implementation scheme willbe described below.

A UE may receive data from a plurality of UEs concurrently. The UE whichreceives the data maintains one or more radio bearers for a datareception. Here, each radio bearer is for receiving data from adifferent <source identifier, destination ID/LCID>. Here, the user planeprotocol stack is identical to a user plane protocol stack illustratedin FIGS. 5A and 5B, so a detailed description will be omitted herein.

In this case, a UE establishes a default radio bearer using defaultconfiguration if the upper layer entity triggers to monitor D2Dcommunication. The established default radio bearer is identified by a<source identifier=null, destination ID/LCID=null>. The UE may alsoestablish a plurality of default radio bearers, one for broadcast, onefor unicast and one or more for associated groups of the UE.

An operating process of a UE in a user plane protocol stackconfiguration scheme #2 for a data reception which is based on thefourth implementation scheme will be described below.

1) Filtering by a physical layer entity using a destination identifierin a scheduling assignment:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein. The destination identifieris transmitted to the MAC layer entity 515 along with the MAC PDU.

2) Filtering by the MAC layer entity 515 using a destination identifierin the MAC PDU:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

3) Determination of a source identifier and Filtering by the MAC layerentity 515 using a source identifier:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

4) The MAC layer entity 515 determines a destination ID or an LCID ofone or more MAC SDUs received in the MAC PDU. The destination ID or theLCID may be determined by reading the destination ID or the LCID from aMAC header of the MAC PDU. In case one part of the destination ID istransmitted in a destination identifier field in the MAC header of theMAC PDU and another part of the destination ID is transmitted inscheduling assignment information, the MAC layer entity 515 determinesthe destination ID by combining both of the parts of the destination ID.

5) For each MAC SDU(s) received in the MAC PDU, the MAC layer entity 515in the UE determines whether there is a radio bearer for a datareception.

a) If there is no radio bearer (i.e. a PDCP layer entity and a RLC layerentity) which is already established except a default radio bearer(s),the MAC layer entity 515 uses the default radio bearer or a defaultradio bearer which is associated with the destination ID. The <sourceidentifier=null, destination ID/LCID=null> is changed to a <sourceidentifier, destination ID/LCID> of the MAC SDU received in the MAC PDU,so the radio bearer becomes a non default radio bearer. The MAC layerentity 515 transmits the MAC SDU the RLC layer entity 513 correspondingto the radio bearer. The MAC layer entity 515 triggers generation of anew default radio bearer.

b) If a non default radio bearer is already established, and if the<source identifier, destination ID/LCID> of the MAC SDU received in theMAC PDU is different from a <source identifier, destination ID/LCID> ofeach of existing radio bearers, the MAC layer entity 515 uses thedefault radio bearer or a default radio bearer which is associated withthe destination ID. The <source identifier=null, destinationID/LCID=null> is changed to the <source identifier, destination ID/LCID>corresponding to the MAC SDU, so the radio bearer becomes a non defaultradio bearer. The MAC layer entity 515 transmits the MAC SDU to the RLClayer entity 513 corresponding to the radio bearer. The MAC layer entity515 also triggers generation of a new default radio bearer.

c) If a radio bearer is already established, and if the <sourceidentifier, destination ID/LCID> included in the MAC SDU is identical toa <source identifier, destination ID/LCID> of an old existing radiobearer, the MAC layer entity 515 transmits the MAC SDU to the RLC layerentity 513.

If there is no activity for a pre-defined time period, the radio bearerfor the data reception is released. The established radio bearer for thedata reception is released if the upper layer entity indicates to stopmonitoring D2D communication.

Meanwhile, if voice service data is received from one TX UE, the MAClayer entity 515 may not establish a radio bearer with another TX UE fora voice service. Alternatively, the UE may release an old voice service,and generate a radio bearer for a voice service with a new TX UE. Here,the radio bearer with the new TX UE may be generated based on TX UEpreference. The UE may identify a voice service using some indicatorincluded in a MAC PDU.

Alternatively, maintenance for a voice service may be processed in theupper layer entity. If the voice service is received from one TX UE,voice service packets from another TX UE may be discarded by the upperlayer entity.

As described above, in a user plane protocol stack configuration scheme#2 for a data reception which is based on each of the firstimplementation scheme to the fourth implementation scheme, a MAC layerentity may indicate a RRC layer entity to generate/release a radiobearer, or may generate/release a new radio bearer.

A user plane protocol stack configuration scheme #2 has been describedabove, and a user plane protocol stack configuration scheme #3 will bedescribed below.

Firstly, a user plane protocol stack configuration scheme #3 for a datatransmission will be described below.

A UE which transmits data maintains a plurality of radio bearers for adata transmission. Each radio bearer refers to one PDCP layer entity andone RLC entity. A different radio bearer is created for a differentdestination. A radio bearer is also different for a different trafficclass for a destination (if needed). Here, the UE may perform aplurality of TX sessions concurrently for the same destination or adifferent destination. The radio bearer is mapped to one logical channelthe logical channel is mapped to a D2D communication transport channelwhich is mapped to a D2D communication broadcast physical channel.

A radio bearer (i.e. a PDCP layer entity and a RLC layer entity) for adata transmission is established/created if a upper layer entitytriggers the data transmission in the UE. A PDCP layer entity and a RLClayer entity are established/created and configured using defaultvalues.

The upper layer entity may indicate whether the data transmission in theUE is a broadcast transmission, a unicast transmission, or a group casttransmission. That is, the upper layer entity may indicate the datatransmission in the UE is the broadcast transmission, the unicasttransmission, or the group cast transmission by transmitting informationwhich indicates that the data transmission in the UE is the broadcasttransmission, the unicast transmission, or the group cast transmission.If the data transmission is the unicast transmission then upper layerentity provides the destination UE ID. If the data transmission is thegroupcast transmission, then upper layer provides the destination GroupID. The UE ID of the UE may also be provided by the upper layer entity.The established/created PDCP layer entity and RLC layer entity areremoved if the upper layer entity stops the data transmission. In theUE, a radio bearer (i.e. a PDCP layer entity and a RLC layer entity)which is established for a data transmission is released if the upperlayer entity triggers release of the radio bearer which is establishedfor the data transmission.

Meanwhile, the radio bearers may be identified as the following.

Each of the radio bearers may be identified by the identifier of itsassociated logical channel, i.e. an LCID. Here, the LCID is local to aUE, and assignment of an LCID to a logical channel of a radio bearer ismaintained by the UE. The LCID is unique assigned across all logicalchannels of radio bearers irrespective of the destination ID to whichdata is transmitted by the radio bearer. If the LCID is used to identifythe radio bearers, the UE includes the LCID into a MAC header during adata transmission. The LCID to a service mapping may be defined, so theUE may identify the service based on the LCID.

Alternately the radio bearers may be identified using a destination IDand a LCID. Here, the LCID is local to a UE, and assignment of an LCIDto a logical channel of a radio bearer is maintained by the UE. The LCIDis unique only across logical channels of radio bearers of the samedestination ID. If the LCID is used to identify the radio bearerstogether with the destination ID, then the UE includes the LCID into aMAC header during a data transmission. The LCID to a service mapping maybe defined, so the UE may identify the service based on the LCID.

During the data transmission, the PDCP layer entity processes packetsreceived from upper layer (i.e. applies a security and/or a headercompression and/or a sequence numbering to the packets) and sends themto a RLC layer entity. The RLC layer entity processes these packets(i.e. RLC SDUs) (applies a sequence numbering and/or a fragmentation)and sends them to a MAC layer entity. The MAC layer entity transmits oneor more of these packets (i.e. MAC SDUs) corresponding to the samedestination ID in the MAC PDU.

During the data transmission, a source identifier and a destinationidentifier are transmitted by the UE and scheme of transmitting them issame as described in user plane protocol stack configuration scheme #1,so a detailed description will be omitted herein.

A user plane protocol stack configuration scheme #3 for a datatransmission has been described above, and a user plane protocol stackconfiguration scheme #3 for a data reception will be described below.

The user plane protocol stack configuration scheme #3 for the datareception is based on one of the first implementation scheme to thefourth implementation scheme, and the user plane protocol stackconfiguration scheme #3 for the data reception which is based on each ofthe first implementation scheme to the fourth implementation scheme willbe described below.

Firstly, a user plane protocol stack configuration scheme #3 for a datareception which is based on the first implementation scheme will bedescribed below.

A UE receives data from one UE at a time. The UE maintains one or moreradio bearers (i.e. PDCP layer entities and RLC layer entities) for adata reception, and each of the radio bearers (i.e. the PDCP layerentities and the RLC layer entities) is for a data reception from thesame UE.

An example of a structure of a user plane protocol stack for a datatransmission and reception which is based on a user plane protocol stackconfiguration scheme #3 in a connectionless communication systemaccording to an embodiment of the present disclosure will be describedwith reference to FIG. 6.

FIG. 6 schematically illustrates an example of a structure of a userplane protocol stack for a data transmission and reception which isbased on a user plane protocol stack configuration scheme #3 in aconnectionless communication system according to an embodiment of thepresent disclosure.

Referring to FIG. 6, it will be noted that a user plane protocol stack600 in FIG. 6 is a user plane protocol stack for data transmissionincluding a plurality of TX radio bearers, i.e. a plurality of PDCPlayer entities 601 and a plurality of RLC layer entities 603, and a userplane protocol stack 610 in FIG. 6 is a user plane protocol stack fordata reception including a plurality of RX radio bearers, i.e. aplurality of PDCP layer entities 611 and a plurality of RLC layerentities 613.

The user plane protocol stack 600 for data transmission includes a PDCPlayer entity #1 601-1 and a RLC layer entity #1 603-1 corresponding to afirst radio bearer #1, includes PDCP layer entity #n 601-n and a RLClayer entity #n 603-n corresponding to a radio bearer #n, and so on. Theuser plane protocol stack 600 for data transmission also includes a MAClayer entity 605 which is common across all of the radio bearers. Eachof the PDCP layer entities 601 and the RLC layer entities 603 areidentified by a LCID, wherein the LCID is unique across the radiobearers. Alternately each of the PDCP layer entities 601 and RLC layerentities 603 are identified by a destination ID and a LCID, wherein theLCID is unique across the radio bearers of the same destination.

The user plane protocol stack 610 for data reception includes a PDCPlayer entity #1 611-1 and a RLC layer entity #1 613-1 corresponding to afirst radio bearer #1, includes a PDCP layer entity #n 611-n and a RLClayer entity #n 613-n corresponding to a radio bearer #n, and so on. Theuser plane protocol stack 610 for data reception also includes a MAClayer entity 615 which is common across all of the radio bearers. Eachof the PDCP layer entities 611 and the RLC layer entities 613 areidentified by a source identifier and a LCID, wherein the LCID isassigned by a transmitting UE such that the LCID is unique across all ofthe radio bearers of the transmitting UE. Each of the PDCP layerentities 611 and the RLC layer entities 613 are identified by a sourceidentifier, a destination ID and a LCID, wherein the LCID is assigned bythe transmitting UE such that the LCID is unique only across the radiobearers (i.e. the PDCP layer entities and the RLC layer entities) of thesame destination in the transmitting UE.

An operating process of a UE in a user plane protocol stackconfiguration scheme #3 for a data reception which is based on the firstimplementation scheme will be described below.

1) Filtering by a physical layer entity using a destination identifierin a scheduling assignment:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein. The destination identifieris transmitted to the MAC layer entity 615 along with the received MACPDU.

2) Filtering by the MAC layer entity 615 using a destination identifierin the MAC PDU:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

3) Determination of a source identifier and Filtering by the MAC layerentity 615 using a source identifier:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

4) The MAC layer entity 615 determines a destination ID and/or an LCIDof one or more MAC SDUs received in the MAC PDU. The destination IDand/or the LCID may be determined by reading the destination ID and/orthe LCID from a MAC header of the MAC PDU. In case one part of thedestination ID is transmitted in a destination identifier field in theMAC header of the MAC PDU and another part of the destination ID istransmitted in scheduling assignment information, the MAC layer entity615 determines the destination ID by combining both of the parts of thedestination ID.

5) For each MAC SDU(s) received in the MAC PDU, the MAC layer entity 615in the UE determines whether there is a radio bearer (i.e. a PDCP layerentity and a RLC layer entity) for data reception.

a) If there is no radio bearer (i.e. a PDCP layer entity and a RLC layerentity) which is already established for a data reception, the MAC layerentity 615 triggers a creation/establishment of a new radio bearer for adata reception, and identifies the new radio bearer (i.e. a PDCP layerentity and a RLC layer entity) for the data reception using the sourceidentifier and an LCID of the MAC SDU received in the MAC PDU.

Alternately, the MAC layer entity 615 identifies the new radio bearer(i.e. the PDCP layer entity and the RLC layer entity) for the datareception using the source identifier, a destination ID and an LCID ofthe MAC SDU received in the MAC PDU. The MAC layer entity 615 transmitsthe MAC SDU to the RLC layer entity 613 corresponding to the new radiobearer.

b) If a radio bearer (i.e. a PDCP layer entity and a RLC layer entity)is already established, and if the source identifier of the MAC SDUreceived in the MAC PDU is different from a source identifier of each ofexisting radio bearers, the MAC layer entity 615 triggers release of theexisting radio bearers (i.e. PDCP layer entities and RLC layerentities), and establishment of a new radio bearer, and identifies aradio bearer (i.e. a PDCP layer entity and a RLC layer entity) using the<source identifier, LCID> of the MAC SDU.

Alternately, the MAC layer entity 615 identifies the new radio bearer(i.e. a PDCP layer entity and a RLC layer entity) for the data receptionusing the <Source Identifier, Destination ID and LCID> of the MAC SDU.The MAC layer entity 615 transmits the MAC SDU to the new RLC layerentity 613 corresponding to the new radio bearer.

c) If a radio bearer is already established for a data reception, and ifthe source identifier and the LCID of the MAC SDU received in the MACPDU is identical to a source identifier and the LCID of an existingradio bearer for a data reception, the MAC layer entity 615 transmitsthe MAC SDU to the RLC layer entity 613 corresponding to the radiobearer. Alternately, If a radio bearer is already established for a datareception, and if the source identifier, a destination ID and an LCID ofthe MAC SDU is identical to a source identifier, a destination ID and anLCID of an existing radio bearer for a data reception, the MAC layerentity 615 transmits the MAC SDU to the RLC layer entity 613corresponding to the existing radio bearer.

d) If a radio bearer is already established, and if the sourceidentifier of the MAC SDU received in the MAC PDU is identical to thesource identifier of the existing radio bearer, and an LCID of the MACSDU is different from an LCID of the existing radio bearer, the MAClayer entity 615 triggers establishment of a new radio bearer, andtransmits the MAC SDU to the RLC layer entity 613 corresponding to thenew radio bearer. Alternately, if a radio bearer is already established,and if the source identifier of the MAC SDU is identical to the sourceidentifier of the existing radio bearer, and an LCID and/or adestination ID of the MAC SDU is different from an LCID and/or adestination ID of the existing radio bearer, the MAC layer entity 615triggers establishment of a new radio bearer, and transmits the MAC SDUto the RLC layer entity 613 corresponding to the new radio bearer.

If there is no activity for a pre-defined time period, the radio bearerfor the data reception is released. The established radio bearer for thedata reception is released if the upper layer entity indicates to stopmonitoring D2D communication.

A user plane protocol stack configuration scheme #3 for a data receptionwhich is based on the first implementation scheme has been describedabove, and a user plane protocol stack configuration scheme #3 for adata reception which is based on the second implementation scheme willbe described below.

A UE receives data from one UE at a time. The UE which receives the datamaintains one or more radio bearers (i.e. PDCP layer entities and RLClayer entities) for a data reception. Here, the user plane protocolstack is identical to a user plane protocol stack illustrated in FIG. 6,so a detailed description will be omitted herein.

Firstly, a UE establishes a default radio bearer using defaultconfiguration if a upper layer entity triggers to monitor D2Dcommunication. The established default radio bearer may be identified bya <source identifier=null, LCID=null>. Alternately, the establisheddefault radio bearer may be identified by a <source identifier=null,destination ID=null, LCID=null>. The UE may also establish a pluralityof default radio bearers. The plurality of default radio bearers may befor a different destination ID, different services, or a differentdestination ID and different services. Here, one of the plurality of thedefault radio bearers is for broadcast, one for unicast, and one or morefor associated groups. The other services denote services which havedifferent priorities such as a voice service and a data service.

An operating process of a UE in a user plane protocol stackconfiguration scheme #3 for a data reception which is based on thesecond implementation scheme will be described below.

1) Filtering by a physical layer entity using a destination identifierin a scheduling assignment:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein. The destination identifieris transmitted to the MAC layer entity 615 along with the received MACPDU.

2) Filtering by the MAC layer entity 615 using a destination identifierin the MAC PDU:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

3) Determination of a source identifier and Filtering by the MAC layerentity 615 using a source identifier:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

4) The MAC layer entity 615 determines a destination ID and/or an LCIDof one or more MAC SDUs received in the MAC PDU. The destination IDand/or the LCID may be determined by reading the destination ID and/orthe LCID from a MAC header of the MAC PDU. In case one part of thedestination ID is transmitted in a destination identifier field in theMAC header of the MAC PDU and another part of the destination ID istransmitted in scheduling assignment information, the MAC layer entity615 determines the destination ID by combining both of the parts of thedestination ID.

5) For each MAC SDU(s) received in the MAC PDU, the MAC layer entity 615in the UE determines whether there is a radio bearer (i.e. a PDCP layerentity and a RLC layer entity) for data reception.

a) If there is no radio bearer (i.e. a PDCP layer entity and a RLC layerentity) which is already established except default radio bearers for adata reception, the MAC layer entity 615 uses the default radio bearers,a default radio bearer which is associated with a destination ID, adefault radio bearer which is associated with a service of a MAC SDUreceived in the MAC PDU, or a default radio bearer which is associatedwith a service of the MAC PDU and the destination ID. The <sourceidentifier=null, LCID=null> is changed to a <source identifier, LCID>corresponding to the MAC SDU, so the default radio bearer becomes a nondefault radio bearer.

Alternately, the <source identifier=null, Destination ID=null LCID=null>is changed to a <source identifier, Destination ID, LCID> correspondingto the MAC PDU, so the default radio bearer becomes a non default radiobearer. The MAC layer entity 615 transmits the MAC SDU to the RLC layerentity 613 corresponding to the radio bearer. The MAC layer entity 615also triggers generation of a new default radio bearer with samecharacteristics as the default bearer which is already used.

b) If a non default radio bearer is already established, and if a sourceidentifier of the MAC SDU received in the MAC PDU is different from asource identifier of each of existing non default radio bearers, the MAClayer entity 615 triggers release of the existing non default radiobearers. The MAC layer entity 615 uses the default radio bearer, adefault radio bearer which is associated with the destination ID, adefault bearer which is associated with a service of the MAC SDU, or adefault bearer which is associated with the destination ID and a serviceof the MAC SDU. The <source identifier=null, LCID=null> is changed to a<source identifier, LCID> corresponding to the MAC SDU, so the defaultradio bearer becomes a non default radio bearer.

Alternately, the <source identifier=null, Destination ID=null LCID=null>is changed to a <source identifier, Destination ID, LCID> correspondingto the MAC SDU, so the default radio bearer becomes a non default radiobearer. The MAC layer entity 615 transmits the MAC SDU to the RLC layerentity 613 corresponding to the radio bearer. The MAC layer entity 615also triggers generation of a new default radio bearer with samecharacteristics as the default bearer which is already used.

c) If a non default radio bearer is already established, and if a sourceidentifier of a MAC SDU received in the MAC PDU is identical to a sourceidentifier of an existing non default radio bearer, and an LCID of theMAC SDU is identical to an LCID of the existing non default radiobearer, the MAC layer entity 615 transmits the MAC SDU to the RLC layerentity 613 corresponding to the radio bearer.

Alternately, If a non default radio bearer is already established, andif a source identifier of the MAC SDU is identical to a sourceidentifier of an existing non default radio bearer, and a LCID and adestination ID of the MAC SDU is identical to a LCID and a DestinationID of the existing non default radio bearer, the MAC layer entity 615transmits the MAC SDU to the RLC layer entity 613 corresponding to theexisting non default radio bearer.

d) If a radio bearer is already established, and if a \source identifierof a MAC SDU received in the MAC PDU is identical to a source identifierof an existing non default radio bearer and a LCID of MAC PDU isdifferent from a LCID of the existing non default radio bearer, then theMAC layer entity 615 uses a default radio bearer, that is a defaultradio bearer which is associated with a destination ID, a default radiobearer which is associated with the received MAC SDU, or a default radiobearer which is associated with the destination ID and the MAC SDU.

Alternately, If a radio bearer is already established, and if a sourceidentifier of the MAC SDU is identical to a source identifier of anexisting non default radio bearer and a LCID or a destination ID of theMAC SDU is different from a LCID or a destination ID of the existing nondefault radio bearer, then the MAC layer entity 615 uses a default radiobearer, that is a default radio bearer which is associated with adestination ID, a default radio bearer which is associated with the MACSDU, or a default radio bearer which is associated with the destinationID and the MAC SDU. The <source identifier=null, LCID=null> is changedto a <source identifier, LCID> corresponding to the MAC SDU, so thedefault radio bearer becomes a non default radio bearer.

Alternately, the <source identifier=null, Destination ID=null LCID=null>is changed to a <source identifier, Destination ID, LCID> correspondingto the MAC PDU, so the default radio bearer becomes a non default radiobearer. The MAC layer entity 615 transmits the MAC SDU to the RLC layerentity 613 corresponding to the radio bearer. The MAC layer entity 615also triggers generation of a new default radio bearer with samecharacteristics as the default bearer which is already used.

If there is no activity for a pre-defined time period, the non defaultradio bearer for the data reception is released, and a default radiobearer is established with default configuration. The establisheddefault radio bearer and the established non default radio bearer forthe data reception are released if the upper layer entity indicates tostop monitoring D2D communication.

A user plane protocol stack configuration scheme #3 for a data receptionwhich is based on the second implementation scheme has been describedabove, and a user plane protocol stack configuration scheme #3 for adata reception which is based on the third implementation scheme will bedescribed below.

A UE may receive data from a plurality of TX UEs concurrently. The UEmay maintain one or more radio bearers (i.e. PDCP layer entities and RLClayer entities) for a data reception. Each radio bearer is for a datareception from a different <source identifier, LCID> or from a different<source identifier, Destination ID, LCID>.

Another example of a structure of a user plane protocol stack for a datatransmission and reception which is based on a user plane protocol stackconfiguration scheme #3 in a connectionless communication systemaccording to an embodiment of the present disclosure will be describedwith reference to FIGS. 7A and 7B.

FIGS. 7A and 7B schematically illustrate another example of a structureof a user plane protocol stack for a data reception which is based on auser plane protocol stack configuration scheme #3 in a connectionlesscommunication system according to an embodiment of the presentdisclosure.

Referring to FIGS. 7A & 7B, it will be noted that a user plane protocolstack 700 in FIG. 7A is a user plane protocol stack for datatransmission including a plurality of TX radio bearers, i.e. a pluralityof PDCP layer entities 701 and a plurality of RLC layer entities 703,and a user plane protocol stack 710 in FIG. 7B is a user plane protocolstack for data reception including a plurality of RX radio bearers, i.e.a plurality of PDCP layer entities 711 and a plurality of RLC layerentities 713.

The user plane protocol stack 700 for data transmission includes a PDCPlayer entity #1 701-1 and a RLC layer entity #1 703-1 corresponding to afirst radio bearer #1, includes PDCP layer entity #n 701-n and a RLClayer entity #n 703-n corresponding to a radio bearer #n, and so on. Theuser plane protocol stack 700 for data transmission also includes a MAClayer entity 705 which is common across all of the radio bearers. ThePDCP layer entity 701 and RLC layer entity 703 are identified by a LCID,wherein the LCID is unique across the radio bearers. Alternately, eachof the PDCP layer entities 701 and the RLC layer entities 703 areidentified by a destination ID and a LCID, wherein the LCID is uniqueacross the radio bearers of the same destination.

The user plane protocol stack 710 for data reception includes a PDCPlayer entity #1 711-1 and a RLC layer entity #1 713-1 corresponding to afirst radio bearer #1, includes a PDCP layer entity #2 711-2 and a RLClayer entity #2 713-2 corresponding to a radio bearer #2, and so on. Theuser plane protocol stack 710 for data reception also includes a MAClayer entity 715 which is common across all of the radio bearers. Eachof the PDCP layer entities 711 and the RLC layer entities 713 areidentified by a source identifier and a LCID, wherein the LCID isassigned by a transmitting UE such that the LCID is unique across all ofthe radio bearers (i.e. PDCP layer entities and RLC layer entities) ofthe transmitting UE. Each of the PDCP layer entities 711 and the RLClayer entities 713 are identified by a source identifier, a destinationID and a LCID, wherein the LCID is assigned by the transmitting UE suchthat the LCID is unique only across the radio bearers (i.e. the PDCPlayer entities and the RLC layer entities) of the same destination inthe transmitting UE.

An operating process of a UE in a user plane protocol stackconfiguration scheme #3 for a data reception which is based on the thirdimplementation scheme will be described below.

1) Filtering by a physical layer entity using a destination identifierin a scheduling assignment:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein. The destination identifierreceived in scheduling assignment is transmitted to the MAC layer entity715 along with the received MAC PDU.

2) Filtering by the MAC layer entity 715 using a destination identifierin the MAC PDU:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

3) Determination of a source identifier and Filtering by the MAC layerentity 715 using a source identifier:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

4) The MAC layer entity 715 determines a destination ID and/or an LCIDof one or more MAC SDUs received in the MAC PDU. The destination IDand/or the LCID may be determined by reading the destination ID and/orthe LCID from a MAC header of the MAC PDU. In case one part of thedestination ID is transmitted in destination identifier field in the MACheader of the MAC PDU and another part of the destination ID istransmitted in scheduling assignment information, the MAC layer entity715 determines the destination ID by combining both of the parts of thedestination ID.

5) For each MAC SDU(s) received in the MAC PDU, the MAC layer entity 715in the UE determines whether there is a radio bearer (i.e. a PDCP layerentity and a RLC layer entity) for data reception.

a) If there is no radio bearer (i.e. a PDCP layer entity and a RLC layerentity) which is already established/created for a data reception, theMAC layer entity 715 triggers creation/establishment of a new radiobearer (i.e. a PDCP layer entity and a RLC layer entity), and identifiesthe new radio bearer (i.e. the PDCP layer entity and the RLC layerentity) for the data reception using a source identifier and a LCID orusing a source identifier, a destination ID and a LCID of the MAC SDUreceived in the MAC PDU. The MAC layer entity 715 transmits the MAC SDUto to the RLC layer entity 713 corresponding to the new radio bearer.

b) If a radio bearer (i.e. a PDCP layer entity and a RLC layer entity)is already established/created, and if a source identifier and/or a LCIDof a MAC SDU received in the MAC PDU is different from a sourceidentifier and/or a LCID of an already established/created radio bearer(i.e. a PDCP layer entity and a RLC layer entity), the MAC layer entity715 triggers establishment of a new radio bearer (i.e. a PDCP layerentity and a RLC layer entity), and identifies the new radio bearer(i.e. the PDCP layer entity and the RLC layer entity) using a sourceidentifier and a LCID of the MAC SDU.

Alternately, if a radio bearer (i.e. a PDCP layer entity and a RLC layerentity) is already established/created, and if a source identifierand/or a destination ID and/or a LCID of a MAC SDU received in the MACPDU is different from a source identifier and/or a destination ID and/ora LCID of an already established/created radio bearer (i.e. a PDCP layerentity and a RLC layer entity), the MAC layer entity 715 triggers anestablishment of a new radio bearer (i.e. a PDCP layer entity and a RLClayer entity), and identifies the new radio bearer (i.e. the PDCP layerentity and the RLC layer entity) using the source identifier, thedestination ID and the LCID of the MAC SDU. The MAC layer entity 715transmits MAC SDU(s) included in the MAC PDU to the RLC layer entity 713corresponding to the new radio bearer.

c) If a radio bearer (i.e. a PDCP layer entity and a RLC layer entity),is already established/created, and if the source identifier and LCID ofthe MAC SDU received in the MAC PDU is identical to a source identifierand a LCID of established/created radio bearer, the MAC layer entity 715transmits the MAC SDU to the RLC layer entity 713 corresponding to theradio bearer.

Alternately, If a radio bearer (i.e. a PDCP layer entity and a RLC layerentity), is already established/created, and if the source identifierand a destination ID and a LCID of the MAC SDU is identical to a sourceidentifier and a destination ID and a LCID of the established/createdradio bearer, the MAC layer entity 715 transmits the MAC SDU to the RLClayer entity 713 corresponding to the established/created radio bearer.

If there is no activity for a pre-defined time period, the radio bearer(i.e. a PDCP layer entity and a RLC layer entity) for the data receptionis released.

Meanwhile, if a voice service is received from one TX UE, the MAC layerentity 715 may not establish a radio bearer (i.e. a PDCP layer entityand a RLC layer entity) with another TX UE for the voice service.Alternatively, the UE may release an old voice service, and generate aradio bearer (i.e. a PDCP layer entity and a RLC layer entity) for avoice service with a new TX UE. Here, the radio bearer (i.e. a PDCPlayer entity and a RLC layer entity) for the voice service may begenerated based on TX UE preference. The UE may identify a voice serviceusing some indicator included in a MAC PDU.

Alternatively, maintenance for one voice service may be processed in theupper layer entity. If the voice service is received from one TX UE,voice service packets from another TX UE may be discarded by the upperlayer entity.

A user plane protocol stack configuration scheme #3 for a data receptionwhich is based on the third implementation scheme has been describedabove, and a user plane protocol stack configuration scheme #3 for adata reception which is based on the fourth implementation scheme willbe described below.

A UE may receive data from a plurality of TX UEs concurrently. The UEwhich receives the data maintains one or more radio bearers or logicalchannels for a data reception. Each radio bearer or each logical channelis for a data reception from a different <source identifier, LCID> ordifferent <source identifier, Destination ID, LCID>. Here, the userplane protocol stack is identical to a user plane protocol stackillustrated in FIGS. 7A and 7B, so a detailed description will beomitted herein.

The UE establishes a default radio bearer using default configuration ifa upper layer entity triggers to monitor D2D communication. Theestablished default radio bearer is identified by a sourceidentifier=null and LCID=null> or using source identifier=null andDestination ID=null and LCID=null. The UE may also establish a pluralityof default radio bearers. The plurality of default radio bearers may befor a different destination ID, different services, or a differentdestination ID and different services. Here, one of the plurality of thedefault radio bearers may exist for broadcast, one for unicast, and oneor more for associated groups. The other services may be services whichhave different priorities such as a voice service and a data service.The default bearers may be established for a different service for eachdestination ID.

An operating process of a UE in a user plane protocol stackconfiguration scheme #3 for a data reception which is based on thefourth implementation scheme will be described below.

1) Filtering by a physical layer entity using a destination identifierin a scheduling assignment:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein. The destination identifieris transmitted to the MAC layer entity 715 along with the received MACPDU.

2) Filtering by the MAC layer entity 715 using a destination identifierin the MAC PDU:

This is same as explained in the first implementation scheme of the userplane protocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

3) Determination of a source identifier and Filtering by the MAC layerentity 715 using a source identifier:

This is same as explained in first implementation scheme of a user planeprotocol stack configuration scheme #1 for a data reception, so adetailed description will be omitted herein.

4) The MAC layer entity 715 determines a destination ID and/or an LCIDof one or more MAC SDUs received in the MAC PDU. The destination IDand/or the LCID may be determined by reading the destination ID and/orthe LCID from a MAC header of the MAC PDU. In case one part of thedestination ID is transmitted in a destination identifier field in theMAC header of the MAC PDU and another part of the destination ID istransmitted in scheduling assignment information, the MAC layer entity715 determines the destination ID by combining both of the parts of thedestination ID.

5) For each MAC SDU(s) received in the MAC PDU, the MAC layer entity 715in the UE determines whether there is a radio bearer (i.e. a PDCP layerentity and a RLC layer entity) for data reception.

a) If there is no radio bearer (i.e. a PDCP layer entity and a RLC layerentity (which is already established except default radio bearers (i.e.default PDCP layer entities and default RLC layer entities), the MAClayer entity 715 uses the default radio bearer (i.e. the default PDCPlayer entity and the default RLC layer entity), that is a default radiobearer (i.e. a default PDCP layer entity and a default RLC layer entity)which is associated with the destination ID, a default radio bearer(i.e. a default PDCP layer entity and a default RLC layer entity) whichis associated with a service of a MAC SDU received in the MAC PDU, or adefault radio bearer (i.e. a default PDCP layer entity and a default RLClayer entity) which is associated with a service of the MAC SDU and thedestination ID. The source identifier=null, and LCID=null is changed toa source identifier and LCID corresponding to the MAC SDU, so thedefault radio bearer becomes a non default radio bearer.

Alternately, the source identifier=null, Destination ID=null andLCID=null is changed to a source identifier, destination ID and LCIDcorresponding to the MAC SDU, so the default radio bearer becomes a nondefault radio bearer. The MAC layer entity 715 transmits the MAC SDU(s)included in the MAC PDU to the RLC layer entity 713 corresponding to theradio bearer. The MAC layer entity 715 triggers a creation/establishmentof a new default radio bearer. The MAC layer entity 715 also triggers acreation/establishment of a new default radio bearer with samecharacteristics as the default bearer which is used.

b) If a radio bearer (i.e. a PDCP layer entity and a RLC layer entity)is already established, and if the source identifier and/or a LCID ofthe MAC SDU received in the MAC PDU is different from a sourceidentifier and/or a LCID of each of existing radio bearers, the MAClayer entity 715 uses the default radio bearer, a default radio bearerwhich is associated with the destination ID, a default bearer which isassociated with a service of the MAC SDU, or a default bearer which isassociated with the destination ID and a service of the MAC SDU. Thesource identifier=null, and LCID=null is changed to a source identifierand LCID corresponding to the MAC SDU, so the default radio bearerbecomes a non default radio bearer.

Alternately, If a radio bearer (i.e. a PDCP layer entity and a RLC layerentity) is already established, and if the source identifier and/or thedestination ID and/or the LCID of the MAC SDU received in the MAC PDU isdifferent from a source identifier and/or a destination ID and/or a LCIDof each of existing radio bearers, the MAC layer entity 715 uses adefault radio bearer, that is a default radio bearer which is associatedwith the destination ID, a default bearer which is associated with aservice of the MAC SDU, or a default bearer which is associated with thedestination ID and a service of the MAC SDU. The source identifier=null,Destination ID=null and LCID=null is changed to a source identifier,destination ID and LCID corresponding to the MAC SDU, so the defaultradio bearer becomes a non default radio bearer. The MAC layer entity715 transmits the MAC SDU to the RLC layer entity 713 corresponding tothe default radio bearer. The MAC layer entity 715 also triggersgeneration of a new default radio bearer (i.e a PDCP layer entity and aRLC layer entity) with same characteristics as the default bearer whichis used.

c) If a radio bearer (i.e. a PDCP layer entity and a RLC layer entity)is already established, and if the source identifier and the LCID of theMAC SDU received in the MAC PDU is identical to the source identifierand the LCID of the existing radio bearer, the MAC layer entity 715transmits the MAC SDU to the RLC layer entity 713 corresponding to theexisting radio bearer.

Alternately, if a radio bearer (i.e. a PDCP layer entity and a RLC layerentity) is already established, and if the source identifier, thedestination ID and the LCID of the MAC SDU is identical to the sourceidentifier, the destination ID and the LCID of the existing radiobearer, the MAC layer entity 715 transmits the MAC SDU to the RLC layerentity 713 corresponding to the existing radio bearer.

If there is no activity for a pre-defined time period, the radio bearer(i.e. the PDCP layer entity and the RLC layer entity) for the datareception is released. The established default radio bearer (i.e. adefault PDCP layer entity and a default RLC layer entity) and theestablished non default radio bearer (i.e. a non default PDCP layerentity and a non default RLC layer entity) for the data reception arereleased if the upper layer entity indicates to stop monitoring D2Dcommunication.

Meanwhile, if a voice service is received from one TX UE, the MAC layerentity 715 may not establish a radio bearer (i.e. a PDCP layer entityand a RLC layer entity) with another TX UE for a voice service.Alternatively, the UE may release an old voice service, and generate aradio bearer (i.e. a PDCP layer entity and a RLC layer entity) for avoice service with a new TX UE. Here, the radio bearer (i.e. the PDCPlayer entity and the RLC layer entity) for the voice service may begenerated based on TX UE preference. The UE may identify a voice serviceusing some indicator included in a MAC PDU.

Alternatively, maintenance for one voice service may be processed in theupper layer entity. If the voice service is received from one TX UE,voice packets from another TX UE may be discarded by the upper layerentity.

A process of initializing a radio link control (RLC) serial number (SN)in the RLC layer entity when the RLC layer entity is created for datareception will be described below.

In a user plane protocol stack configuration scheme #1, a user planeprotocol stack configuration scheme #2, and a user plane protocol stackconfiguration scheme #3, when a RLC Unacknowledged Mode (UM) or a RLCAcknowledged Mode (AM) entity is created for data reception, thenreceive state variable number VR(UR) is initialized to SN of firstreceived PDU. The receive state variable number VR(UR) holds the valueof the SN of the earliest PDU that is still considered for reordering.

When a RLC Unacknowledged Mode (UM) or a RLC Acknowledged Mode (AM)entity is created for D2D data reception, the receive state variablenumber VR(UH) is initialized to the SN of a first received PDU. Thereceive state variable number VR(UH) holds the value of the SN followingthe SN of the UMD PDU with the highest SN among received UMD PDUs, andit serves as the higher edge of the reordering window.

A robust header compression (ROHC) scheme in a unidirectional mode(U-mode) for 1: M communication will be described below.

In a UM, the ROHC scheme transits periodically from a no compressionstate, e.g., an initialization and refresh (IR) state to a lowcompression state, e.g., a first order (FO) state and a high compressionstate, e.g., a second order (SO) state.

In a group cast, a new receiving UE (RX UE) may join a data session anytime. As a result, the new RX UE may not be able to decompress datapackets until a compressor transits to the no compressor state in a TXUE. So, a period of transitions among states in the ROHC scheme may beset relatively short for preventing that a period during whichcompression for a data packet is interrupt becomes long. However,transitions among states with a relatively short period will lead tovery low compression efficiency.

So, in an embodiment of the present disclosure, if a new RX UE joins adata session, and is not able to decompress data, an indication istransmitted to a TX UE by a PDCP layer entity of the new RX UE. Here,the indication may be transmitted using fixed time/frequency resources,fixed physical layer entity parameters, and a fixed content. Even if aplurality of new RX UEs transmit the indication, there is no issue as aTX UE will decode the fixed time/frequency resources. Upon receiving theindication, the TX UE transits into a no compression state, or transmitsuncompressed packets during some duration.

In at least some of a user plane protocol stack configuration scheme #1to a user plane protocol stack configuration scheme #3, a source UE IDis encoded in source identifier field and a destination ID or a part ofthe destination ID is encoded into a destination identifier field in aMAC header of a MAC PDU. The source UE ID and the destination ID or thepart of the destination ID may be included in the MAC header using oneof the first implementation scheme to the fifth implementation scheme,and this will be described below.

Firstly, a process of including a source UE ID and a destination ID intoa MAC header using the first implementation scheme in a connectionlesscommunication system according to an embodiment of the presentdisclosure will be described below.

In a connectionless communication system according to an embodiment ofthe present disclosure, a MAC header includes at least one MACsub-header. Each MAC sub-header included in the MAC header correspondsto a MAC control element (CE) or a MAC SDU included in a payloadincluded in a MAC PDU, or indicates padding. The MAC sub-header includesan LCID field which identifies a type of a MAC CE or a logical channelwhich is associated with the MAC SDU, or identifies that the MACsub-header is a padding sub-header.

In an embodiment of the present disclosure, a new type of MAC sub-headerindicating a source UE ID and a destination ID is defined, and this willbe described with reference to FIG. 8.

FIG. 8 schematically illustrates an example of a format of a MACsub-header indicating a source UE ID and a destination ID in aconnectionless communication system according to an embodiment of thepresent disclosure.

Referring to FIG. 8, the MAC sub-header includes a R field, an E field,an LCID field, a source identifier field, and a destination identifierfield.

The R field represents a reserved field, the E field includesinformation indicating whether there is other MAC sub-header followingthe MAC sub-header, the LCID field includes information indicating thatthe MAC sub-header carriers a source identifier and a destinationidentifier fields, the source identifier field includes the source UEID, and the destination identifier field includes the destination ID orpart of destination ID.

Meanwhile, a location of the MAC sub-header indicating the source UE IDand the destination ID or a part of the destination ID may be determinedbased on the following rules.

Firstly, if there is no padding in the MAC PDU, or if a length of thepadding is more than a preset length, e.g., 2 bytes, the MAC sub-headerindicating the source UE ID and the destination ID or a part of thedestination ID may be the first MAC sub-header among MAC sub-headersincluded in the MAC PDU.

Secondly, if the length of the padding included in the MAC PDU is thepreset length, e.g., 1 byte, the MAC sub-header indicating the source UEID and the destination ID or a part of the destination ID may be thesecond MAC sub-header among the MAC sub-headers included in the MAC PDU.In this case, the first MAC sub-header among the MAC sub-headersincluded in the MAC PDU is a padding sub-header.

Thirdly, if the length of the padding included in the MAC PDU is thepreset length, e.g., 2 bytes, the MAC sub-header indicating the sourceUE ID and the destination ID or a part of the destination ID may be thethird MAC sub-header among the MAC sub-headers included in the MAC PDU.In this case, the first and second MAC sub-headers among the MACsub-headers included in the MAC PDU are padding sub-headers.

An example of a format of a MAC sub-header indicating a source UE ID anda destination ID or a part of the destination ID in a connectionlesscommunication system according to an embodiment of the presentdisclosure has been described with reference to FIG. 8, and a format ofa MAC sub-header indicating a source UE ID in a connectionlesscommunication system according to an embodiment of the presentdisclosure will be described with reference to FIG. 9A.

FIG. 9A schematically illustrates a format of a MAC sub-headerindicating a source UE ID in a connectionless communication systemaccording to an embodiment of the present disclosure.

Referring to FIG. 9A, the MAC sub-header includes a R field, an E field,an LCID field, and a source identifier field.

The R field represents a reserved field, the E field includesinformation indicating whether there is other MAC sub-header followingthe MAC sub-header, the LCID field includes information indicating thatthe MAC sub-header carriers a source identifier field and the sourceidentifier field includes the source UE ID.

In FIG. 9A, the LCID field includes the information indicating that theMAC sub-header carriers the source identifier. However, it will beunderstood by those of ordinary skill in the art that the LCID field mayinclude information indicating one of that the MAC sub-header carriersthe source UE ID, that the MAC sub-header carriers the destination ID,and that the MAC sub-header carriers the source UE ID and thedestination ID.

A format of a MAC sub-header indicating a source UE ID in aconnectionless communication system according to an embodiment of thepresent disclosure has been described with reference to FIG. 9A, and aformat of a MAC sub-header indicating a destination ID in aconnectionless communication system according to an embodiment of thepresent disclosure will be described with reference to FIG. 9B.

FIG. 9B schematically illustrates a format of a MAC sub-headerindicating a destination ID in a connectionless communication systemaccording to an embodiment of the present disclosure.

Referring to FIG. 9B, the MAC sub-header includes a R field, an E field,an LCID field, and a destination identifier field.

The R field represents a reserved field, the E field includesinformation indicating whether there is other MAC sub-header followingthe MAC sub-header, the LCID field includes information indicating thatthe MAC sub-header carriers a destination identifier field, and thedestination identifier field includes the destination ID or part ofdestination ID.

In FIG. 9B, the LCID field includes the information indicating that theMAC sub-header carriers the destination ID. However, it will beunderstood by those of ordinary skill in the art that the LCID field mayinclude information indicating one of that the MAC sub-header carriersthe source ID, that the MAC sub-header carriers the destination ID, andthat the MAC sub-header carriers the source UE ID and the destinationID.

A process of including a source UE ID and a destination ID into a MACheader using the first implementation scheme in a connectionlesscommunication system according to an embodiment of the presentdisclosure has been described above, and a process of including a sourceUE ID and a destination ID into a MAC header using the secondimplementation scheme in a connectionless communication system accordingto an embodiment of the present disclosure will be described below.

In a connectionless communication system according to an embodiment ofthe present disclosure, a MAC header includes a source identifier field,a destination identifier field, and a MAC PDU format version numberfield. These fields are included in a D2D subheader, and the D2Dsubheader is always included in a beginning of the MAC header. The otherMAC subheaders indicating a MAC CE or MAC SDUs or padding follows theD2D subheader.

An example of a format of a MAC header indicating a source identifierfield, a destination identifier field, and a MAC PDU format versionnumber field in a connectionless communication system according to anembodiment of the present disclosure will be described with reference toFIG. 10. The MAC PDU format version number field indicates which versionof the D2D-SCH subheader is used.

FIG. 10 schematically illustrates an example of a format of a MAC headerindicating a source UE ID and a destination ID in a connectionlesscommunication system according to an embodiment of the presentdisclosure.

Referring to FIG. 10, the MAC header includes a D2D subheader and MACsub-headers. The D2D subheader includes a MAC PDU format version numberfield, a source identifier field, and a destination identifier field.The source identifier field includes a source UE ID, and the destinationidentifier field includes a destination ID or a part of the destinationID. The MAC sub-headers include one or more subheaders indicating atleast one of a MAC CE, MAC SDUs, and padding.

An example of a format of a MAC header indicating a source ID and adestination ID in a connectionless communication system according to anembodiment of the present disclosure has been described with referenceto FIG. 10, and another example of a format of a MAC header indicating asource UE ID and a destination ID or a part of the destination ID in aconnectionless communication system according to an embodiment of thepresent disclosure will be described with reference to FIG. 11A.

FIG. 11A schematically illustrates another example of a format of a MACheader indicating a source UE ID and a destination ID or a part of thedestination ID in a connectionless communication system according to anembodiment of the present disclosure.

Referring to FIG. 11A, it will be noted that a MAC header in FIG. 11A isa MAC header in a case that one byte padding is considered. The MACheader includes a D2D subheader, a padding sub-header, and MACsub-headers. The D2D subheader includes a MAC PDU format version numberfield, a source identifier field, and a destination identifier field.The padding subheader is present after the D2D subheader and before MACsub-headers. The source identifier field includes a source UE ID, andthe destination identifier field includes a destination ID or a part ofthe destination ID. The padding sub-header includes padding. Here, thepadding sub-header is included in the MAC header thereby being locatedbefore the MAC sub-headers. The MAC sub-headers include one or moresubheaders indicating at least one of a MAC CE and MAC SDUs.

Another example of a format of a MAC header indicating a source UE IDand a destination ID or a part of the destination ID in a connectionlesscommunication system according to an embodiment of the presentdisclosure has been described with reference to FIG. 11A, and stillanother example of a format of a MAC header indicating a source UE IDand a destination ID or a part of the destination ID in a connectionlesscommunication system according to an embodiment of the presentdisclosure will be described with reference to FIG. 11B.

FIG. 11B schematically illustrates still another example of a format ofa MAC header indicating a source UE ID and a destination ID or a part ofthe destination ID in a connectionless communication system according toan embodiment of the present disclosure.

Referring to FIG. 11B, it will be noted that a MAC header in FIG. 11B isa MAC header in a case that two-byte padding is considered. The MACheader includes a D2D subheader, two padding sub-headers, and MACsub-headers. The D2D subheader includes a MAC PDU format version numberfield, a source identifier field, and a destination identifier field.The padding subheader is present after the D2D subheader and before MACsub-headers. The source identifier field includes a source UE ID, andthe destination identifier field includes a destination ID or a part ofthe destination ID. The padding sub-header includes padding. Here, thepadding sub-header is included in the MAC header thereby being locatedbefore the MAC sub-headers. The MAC sub-headers include one or moresubheader indicating at least one of a MAC CE and MAC SDUs.

A process of including a source UE ID and a destination ID or a part ofthe destination ID into a MAC header using the second implementationscheme in a connectionless communication system according to anembodiment of the present disclosure has been described above, and aprocess of including a source UE ID and a destination ID or a part ofthe destination ID into a MAC header using the third implementationscheme in a connectionless communication system according to anembodiment of the present disclosure will be described below.

In a connectionless communication system according to an embodiment ofthe present disclosure, a MAC Control Element (CE) which carries asource UE ID and a destination ID or a part of the destination ID isdefined. The MAC CE is indicated by a MAC sub-header, and the MACsub-header includes an LCID field. The LCID field includes informationindicating whether a related MAC CE is a MAC CE including the source UEID and the destination ID. The MAC CE including the source UE ID and thedestination ID may be the first MAC CE field included in a MAC PDUpayload. Alternatively, two MAC CEs wherein one includes the source UEID and another includes the Destination ID is defined.

A process of including a source ID and a destination ID into a MACheader using the third implementation scheme in a connectionlesscommunication system according to an embodiment of the presentdisclosure has been described above, and a process of including a sourceID and a destination ID into a MAC header using the fourthimplementation scheme in a connectionless communication system accordingto an embodiment of the present disclosure will be described below.

In a connectionless communication system according to an embodiment ofthe present disclosure, a MAC header includes at least one MACsub-header. The MAC sub-header indicates a source UE ID and at least apart of a destination ID, and this will be described with reference toFIG. 12.

FIG. 12 schematically illustrates another example of a format of a MACsub-header indicating a source UE ID and at least a part of adestination ID in a connectionless communication system according to anembodiment of the present disclosure.

Referring to FIG. 12, the MAC sub-header includes a BI field, a R field,an E field, an LCID field, a source identifier field, and a destinationidentifier field.

The BI field includes information indicating whether the destinationidentifier field is included in the MAC sub-header, and may beimplemented with 1 bit. If a value of the BI field is set to 1, the MACsub-header does not include the destination identifier field. If a valueof the BI field is set to 0, the MAC sub-header includes the destinationidentifier field.

The R field represents a reserved field, the E field includesinformation indicating whether there is other MAC sub-header followingthe MAC sub-header, the LCID field includes information indicating thatthe MAC sub-header carriers a source UE ID and at least a part of adestination ID, the source identifier field includes the source UE ID,and the destination identifier field includes at least a part of thedestination ID.

Meanwhile, a location of the MAC sub-header indicating the source UE IDand at least a part of the destination ID may be determined based on thefollowing rules.

Firstly, if there is no padding in the MAC PDU, or if a length of thepadding is more than a preset length, e.g., 2 bytes, the MAC sub-headerindicating the source UE ID and at least a part of the destination IDmay be the first MAC sub-header among MAC sub-headers included in theMAC PDU.

Secondly, if the length of the padding included in the MAC PDU is thepreset length, e.g., 1 byte, the MAC sub-header indicating the source UEID and at least a part of the destination ID may be the second MACsub-header among the MAC sub-headers included in the MAC PDU. In thiscase, the first MAC sub-header among the MAC sub-headers included in theMAC PDU is a padding sub-header.

Thirdly, if the length of the padding included in the MAC PDU is thepreset length, e.g., 2 bytes, the MAC sub-header indicating the sourceUE ID and at least a part of the destination ID may be the third MACsub-header among the MAC sub-headers included in the MAC PDU. In thiscase, the first and second MAC sub-headers among the MAC sub-headersincluded in the MAC PDU are padding sub-headers.

A process of including a source UE ID and at least a part of adestination ID into a MAC header using the fourth implementation schemein a connectionless communication system according to an embodiment ofthe present disclosure has been described above, and a process ofincluding a source UE ID and at least a part of a destination ID into aMAC header using the fifth implementation scheme in a connectionlesscommunication system according to an embodiment of the presentdisclosure will be described below.

In a connectionless communication system according to an embodiment ofthe present disclosure, a MAC header includes at least one MACsub-header. The MAC sub-header indicates a source UE ID and at least apart of a destination ID, and this will be described with reference toFIG. 13.

FIG. 13 schematically illustrates still another example of a format of aMAC sub-header indicating a source UE ID and at least a part of adestination ID in a connectionless communication system according to anembodiment of the present disclosure.

Referring to FIG. 13, the MAC sub-header includes an AI field, an Efield, an LCID field, a source identifier field, and a destinationidentifier field.

The AI field includes information indicating one of that the destinationidentifier field is set to a group ID, that the destination identifierfield is set to a destination ID, and that the destination identifierfield is not set to any value.

The E field includes information indicating whether there is other MACsub-header following the MAC sub-header, the LCID field includesinformation indicating that the MAC sub-header carriers a source UE IDand at least a part of a destination ID, the source identifier fieldincludes the source UE ID, and the destination identifier field includesa group ID or at least a part of the destination ID based on a value ofthe AI field, or does not include any value.

A process of including a source UE ID and at least a part of adestination ID into a MAC header using the fifth implementation schemein a connectionless communication system according to an embodiment ofthe present disclosure has been described above, and an inner structureof a BS in a connectionless communication system according to anembodiment of the present disclosure will be described with reference toFIG. 14.

FIG. 14 schematically illustrates an inner structure of a BS in aconnectionless communication system according to an embodiment of thepresent disclosure.

Referring to FIG. 14, a BS 1400 includes a transmitter 1411, acontroller 1413, a receiver 1415, and a storage unit 1417.

The controller 1413 controls the overall operation of the BS 1400. Moreparticularly, the controller 1413 controls the BS 1400 to perform anoperation related to a user plane protocol stack operating operation.The operation related to the user plane protocol stack operatingoperation is performed in the manner described with reference to FIGS. 2to 13, and a description thereof will be omitted herein.

The transmitter 1411 transmits various signals, various messages, andthe like to a UE, and the like under a control of the controller 1413.The various signals, the various messages, and the like transmitted inthe transmitter 1411 have been described in FIGS. 2 to 13, and adescription thereof will be omitted herein.

The receiver 1415 receives various signals, various messages, and thelike from the UE, and the like under a control of the controller 1413.The various signals, the various messages and the like received in thereceiver 1415 have been described in FIGS. 2 to 13, and a descriptionthereof will be omitted herein.

The storage unit 1417 stores a program and various data necessary forthe operation of the BS 1400, information related to the user planeprotocol stack operating operation according to an embodiment of thepresent disclosure, and the like. The storage unit 1417 stores thevarious signals, the various messages, and the like received in thereceiver 1415.

While the transmitter 1411, the controller 1413, the receiver 1415, andthe storage unit 1417 are described as separate processors, it is to beunderstood that this is merely for convenience of description. In otherwords, two or more of the transmitter 1411, the controller 1413, thereceiver 1415, and the storage unit 1417 may be incorporated into asingle processor.

An inner structure of a BS in a connectionless communication systemaccording to an embodiment of the present disclosure has been describedwith reference to FIG. 14, and an inner structure of a UE in aconnectionless communication system according to an embodiment of thepresent disclosure will be described with reference to FIG. 15.

FIG. 15 schematically illustrates an inner structure of a UE in aconnectionless communication system according to an embodiment of thepresent disclosure.

Referring to FIG. 15, a UE 1500 includes a transmitter 1511, acontroller 1513, a receiver 1515, and a storage unit 1517.

The controller 1513 controls the overall operation of the UE 1500. Moreparticularly, the controller 1513 controls the UE 1500 to perform anoperation related to a user plane protocol stack operating operation.The operation related to the user plane protocol stack operatingoperation is performed in the manner described with reference to FIGS. 2to 13, and a description thereof will be omitted herein.

The transmitter 1511 transmits various signals, various messages, andthe like to a BS, and the like under a control of the controller 1513.The various signals, the various messages, and the like transmitted inthe transmitter 1511 have been described in FIGS. 2 to 13, and adescription thereof will be omitted herein.

The receiver 1515 receives various signals, various messages, and thelike from the BS, and the like under a control of the controller 1513.The various signals, the various messages and the like received in thereceiver 1515 have been described in FIGS. 2 to 13, and a descriptionthereof will be omitted herein.

The storage unit 1517 stores a program and various data necessary forthe operation of the UE 1500, information related to the user planeprotocol stack operating operation according to an embodiment of thepresent disclosure, and the like. The storage unit 1517 stores thevarious signals, the various messages, and the like received in thereceiver 1515.

While the transmitter 1511, the controller 1513, the receiver 1515, andthe storage unit 1517 are described as separate processors, it is to beunderstood that this is merely for convenience of description. In otherwords, two or more of the transmitter 1511, the controller 1513, thereceiver 1515, and the storage unit 1517 may be incorporated into asingle processor.

As is apparent from the foregoing description, an embodiment of thepresent disclosure enables to operate a user plane protocol stack in aconnectionless communication system.

An embodiment of the present disclosure enables to operate a user planeprotocol stack by considering a radio bearer in a connectionlesscommunication system.

An embodiment of the present disclosure enables to operate a user planeprotocol stack by considering a logical channel in a connectionlesscommunication system.

An embodiment of the present disclosure enables to operate a user planeprotocol stack based on a source UE ID and at least a part of adestination ID in a connectionless communication system.

An embodiment of the present disclosure enables to operate a user planeprotocol stack based on a transmission session type in a connectionlesscommunication system.

An embodiment of the present disclosure enables to operate a user planeprotocol stack by considering data compression in a connectionlesscommunication system.

Certain aspects of the present disclosure may also be embodied ascomputer readable code on a non-transitory computer readable recordingmedium. A non-transitory computer readable recording medium is any datastorage device that can store data, which can be thereafter read by acomputer system. Examples of the non-transitory computer readablerecording medium include read only memory (ROM), random access memory(RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storagedevices, and carrier waves (such as data transmission through theInternet). The non-transitory computer readable recording medium canalso be distributed over network coupled computer systems so that thecomputer readable code is stored and executed in a distributed fashion.In addition, functional programs, code, and code segments foraccomplishing the present disclosure can be easily construed byprogrammers skilled in the art to which the present disclosure pertains.

It can be appreciated that a method and apparatus according to anembodiment of the present disclosure may be implemented by hardware,software and/or a combination thereof. The software may be stored in anon-volatile storage, for example, an erasable or re-writable ROM, amemory, for example, a RAM, a memory chip, a memory device, or a memoryintegrated circuit (IC), or an optically or magnetically recordablenon-transitory machine-readable (e.g., computer-readable), storagemedium (e.g., a compact disk (CD), a digital versatile disk (DVD), amagnetic disk, a magnetic tape, and/or the like). A method and apparatusaccording to an embodiment of the present disclosure may be implementedby a computer or a mobile terminal that includes a controller and amemory, and the memory may be an example of a non-transitorymachine-readable (e.g., computer-readable), storage medium suitable tostore a program or programs including instructions for implementingvarious embodiments of the present disclosure.

The present disclosure may include a program including code forimplementing the apparatus and method as defined by the appended claims,and a non-transitory machine-readable (e.g., computer-readable), storagemedium storing the program. The program may be electronicallytransferred via any media, such as communication signals, which aretransmitted through wired and/or wireless connections, and the presentdisclosure may include their equivalents.

An apparatus according to an embodiment of the present disclosure mayreceive the program from a program providing device which is connectedto the apparatus via a wire or a wireless and store the program. Theprogram providing device may include a memory for storing instructionswhich instruct to perform a content protect method which has beenalready installed, information necessary for the content protect method,and the like, a communication unit for performing a wired or a wirelesscommunication with a graphic processing device, and a controller fortransmitting a related program to a transmitting/receiving device basedon a request of the graphic processing device or automaticallytransmitting the related program to the transmitting/receiving device.

While the present disclosure has been shown and described with referenceto various embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present disclosure asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method for device to device (D2D) communicationby a user equipment (UE), the method comprising: receiving controlinformation including a first part of a destination identifier (ID) foridentifying target of data for the D2D communication; filtering packetsat a physical layer of the UE, using the first part of the destinationID; receiving a medium access control (MAC) protocol data unit (PDU)including a MAC header including a second part of the destination ID;and filtering packets at a MAC layer of the UE using the second part ofthe destination ID.
 2. The method of claim 1, wherein the first part ofthe destination ID is a least significant bit (LSB) part of thedestination ID, and the second part of the destination ID is a mostsignificant bit (MSB) part of the destination ID.
 3. The method of claim1, wherein the control information further includes a first part of asource ID, and the MAC PDU further includes a second part of the sourceID.
 4. The method of claim 3, wherein the first part of the source ID isa least significant bit (LSB) part of the source ID, and the second partof the source ID is a most significant bit (MSB) part of the source ID.5. The method of claim 3, wherein the first part of the source ID isused for filtering packets at the physical layer of the UE, and thesecond part of the source ID is used for filtering packets at the MAClayer of the UE.
 6. A user equipment (UE) for device to device (D2D)communication, the UE comprising: a transceiver; and a processor coupledto the transceiver, wherein the processor is configured to: receivecontrol information including a first part of a destination identifier(ID) for identifying target of data for the D2D communication, filterpackets at a physical layer of the UE, using the first part of thedestination ID, receive a medium access control (MAC) protocol data unit(PDU) including a MAC header, and filter packets at a MAC layer of theUE using a second part of the destination ID
 7. The UE of claim 6,wherein the first part of the destination ID is a least significant bit(LSB) part of the destination ID, and the second part of the destinationID is a most significant bit (MSB) part of the destination ID.
 8. The UEof claim 6, wherein the control information further includes a firstpart of a source ID, and the MAC PDU further includes a second part ofthe source ID.
 9. The UE of claim 8, wherein the first part of thesource ID is a least significant bit (LSB) part of the source ID, andthe second part of the source ID is a most significant bit (MSB) part ofthe source ID.
 10. The UE of claim 8, wherein the first part of thesource ID is used for filtering packets at the physical layer of the UE,and the second part of the source ID is used for filtering packets atthe MAC layer of the UE.